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Product listing: GMPS Antibody, UniProt ID P49915 #14602 to HER2/ErbB2 (M45) Antibody, UniProt ID P04626 #3250

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Guanine monophosphate synthase (GMPS) catalyzes the conversion of xanthosine 5’-monophosphate (XMP) into GMP during the final step of de novo guanine nucleotide synthesis. In addition to comprising the building blocks for DNA and RNA, guanine nucleotides also provide GTP for many signaling pathways that are important for multiple cellular processes (1). Chromosomal translocations involving MLL and GMPS is reported in some patients diagnosed with acute myeloid leukemia (2). Research studies indicate that genotoxic stress or nucleotide deprivation prompts translocation of GMPS to the nucleus where it complexes with USP7 and p53 to promote p53 stabilization (3). Additional studies show that the nuclear GMPS-USP7 protein complex deubiquitinates histone H2B in Drosophila (4).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Heterotrimeric guanine nucleotide-binding proteins, G proteins, transduce ligand binding to G protein-coupled receptors (GPCRs) into intracellular responses (1). G proteins are comprised of 3 subunits, alpha (Gα), beta (Gβ), and gamma (Gγ). Upon activation of GPCRs, the receptor promotes the exchange of GDP to GTP of Gα, changing the confirmation of the switch regions within Gα. The receptor bound heterotimeric G protein (inactive) is then released, and dissociates into the GTP-bound Gα (active) monomer and the Gβ/Gγ heterodimer (1,2). Gα activates adenylyl cyclase, which converts ATP to the second messenger cAMP. Gα also activates phosphoinositide-specific phospholipase C (PLC), which catalyzes hydrolysis of the phospholipid of phosphatidylinositol 4,5-biphosphate (PIP2), releasing the second messengers IP3 and 1,2-diacylglycerol (DAG). IP3 activates IP3 receptors to release Ca2+ from the ER. DAG is an activator of protein kinase C (PKC), which in turn activates the Erk1/2 pathway (1,3). The primary function of the Gβ/Gγ heterodimer is to inhibit Gα, although it may also activate second messengers (e.g. PLC pathway) or gate ion channels (e.g. GIRK) (1). Guanine nucleotide-binding protein b3 (GNB3) is an isoform of the b subunit. Research studies have shown that a polymorphism in the GNB3 gene, C825T, is associated with hypertension, obesity, and depression (4).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: GP130 is a signal-transducing subunit shared by the receptors for the IL-6 family of cytokines (1-3). The binding of a ligand to its receptor induces the dimerization of GP130, leading to activation of the Jak tyrosine kinase and to tyrosine phosphorylation of GP130. These events lead to the activation of multiple signal-transduction pathways, such as the Stat, Ras-MAPK and PI3 kinase pathways, whose activation is controlled by distinct regions of GP130 (4-7).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey

Application Methods: Western Blotting

Background: Glucose-6-phosphate isomerase (GPI) is a multi-functional protein belonging to the glucose phosphate isomerase family (1,2). As an intracellular metabolic enzyme, GPI plays a pivotal role in glycolysis and gluconeogenesis by catalyzing the interconversion of D-glucose-6-phosphate and D-fructose-6-phosphate (3). GPI is also secreted, where it functions as a cytokine (referred to as Autocrine Motility Factor, AMF), acting via the E3-ubiquitin-protein ligase AMFR/gp78 (4). In normal tissues, GPI/AMF has been shown to promote both immune cell maturation and neuronal cell survival (5,6). It is also secreted in abundance by some tumor cells (7), where it has been shown to promote tumor cell migration and metastasis (8,9).

$260
100 µl
APPLICATIONS
REACTIVITY
Human

Application Methods: Immunoprecipitation, Western Blotting

Background: Glutathione peroxidase 1 (GPX1) is a cytosolic selenoprotein which reduces hydrogen peroxide to water (1). GPX1 is the most abundant and ubiquitous among the five GPX isoforms identified so far (2). It is an important component in the anti-oxidative defense in cells and is associated with a variety of disease conditions, such as colon cancer (3), coronary artery disease (4) and insulin resistance (1).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: GTPase Regulator Associated with Focal Adhesion Kinase-1 (GRAF1), is a GTPase-activating protein for the small G proteins RhoA and Cdc42 (1). It is composed of an N-terminal BAR domain, a PH domain, a RhoGAP domain, a proline-rich domain, and a C-terminal SH3 domain. GRAF1 contributes to the clathrin-independent carriers/GPI-enriched early endosomal compartments (CLIC/GEEC) pathway, and was the first specific protein component of this endocytic pathway to be discovered (2). GRAF1 was identified as an important protein necessary for adeno-associated virus 2 infection (3). In addition, research studies have linked GRAF1 to mental retardation (4), skeletal muscle differentiation (5), and myeloid leukemia (6,7).

$260
100 µl
APPLICATIONS
REACTIVITY
Human

Application Methods: Peptide ELISA (DELFIA), Western Blotting

Background: Granzymes are a family of serine proteases expressed by cytotoxic T lymphocytes and natural killer (NK) cells and are key components of immune responses to pathogens and transformed cells (1). Granzymes are synthesized as zymogens and are processed into mature enzymes by cleavage of a leader sequence. They are released by exocytosis in lysosome-like granules containing perforin, a membrane pore-forming protein. Granzyme B has the strongest apoptotic activity of all the granzymes as a result of its caspase-like ability to cleave substrates at aspartic acid residues thereby activating procaspases directly and cleaving downstream caspase substrates (2,3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse

Application Methods: Peptide ELISA (DELFIA), Western Blotting

Background: Granzymes are a family of serine proteases expressed by cytotoxic T lymphocytes and natural killer (NK) cells and are key components of immune responses to pathogens and transformed cells (1). Granzymes are synthesized as zymogens and are processed into mature enzymes by cleavage of a leader sequence. They are released by exocytosis in lysosome-like granules containing perforin, a membrane pore-forming protein. Granzyme B has the strongest apoptotic activity of all the granzymes as a result of its caspase-like ability to cleave substrates at aspartic acid residues thereby activating procaspases directly and cleaving downstream caspase substrates (2,3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human

Application Methods: Immunoprecipitation, Western Blotting

Background: The GRB7 family of adaptor proteins consist of GRB7, GRB10 and GRB14, which all contain an amino-terminal proline-rich SH3 binding domain, followed by PH, PBS, and SH2 domains. Each member of the family has several splice variants (1). It has been reported that GRB10 interacts with many receptor tyrosine kinases (RTKs) as well as downstream signal molecules including Raf, Akt, and Nedd4 (1,2). Although it was originally thought that GRB10 is exclusively phosphorylated at serine residues (3), Src kinase family members have been shown to phosphorylate GRB10 at Tyr67 (4).

$260
100 µl
APPLICATIONS
REACTIVITY
Bovine, Hamster, Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Growth factor receptor-binding protein 2 (GRB2) is an adaptor protein that is involved in RTK signal transduction. The SH2 domain of GRB2 binds to tyrosine phosphorylated proteins such as EGFR, IRS-1, Shc and Gab1 (1). The SH3 domain of GRB2 associates with Sos, which stimulates the GTP binding activity of Ras, leading to the activation of the MAP kinase and other signaling pathways. Phosphorylation of Tyr209 of GRB2 by Bcr-Abl and EGFR abolishes its association with Sos and negatively regulates downstream signaling (2).

$260
100 µl
APPLICATIONS
REACTIVITY
Mouse

Application Methods: Western Blotting

Background: Gremlin is a secreted antagonist of bone morphogenetic proteins that play important roles during development. Gene targeting generates gremlin deficient mice that die shortly after birth due to absent kidneys and defects in lung septation (1-3). Gremlin also plays a role in cardiomyogenesis and angiogenesis (4,5). TGF-β can induce gremlin expression under pathological conditions. Gremlin colocalizes with TGF-β in tubulointerstitial fibrosis associated with chronic allograft nephropathy and is expressed in diabetic nephropathy in vivo (6-8). Gremlin is widely expressed in cancer associated stromal cells and can enhance cancer cell proliferation (9).

$260
100 µl
APPLICATIONS
REACTIVITY
Hamster, Human, Monkey, Mouse, Rat

Application Methods: Immunoprecipitation, Western Blotting

Background: G-protein-coupled receptor kinase 2 (GRK2), also known as beta-adrenergic receptor kinase 1 (beta-ARK1), is a member of the GRK family, which phosphorylates the activated form of G-protein-coupled receptors (GPCRs) and initiates the desensitization process of GPCR (1). GRK2 kinase activity and cellular localization are tightly regulated by interactions with activated receptors, G-beta and G-gamma subunits, adaptor proteins, phospholipids, caveolin and calmodulin, as well as by phosphorylation (1). PKC phosphorylation enhances GRK2 activity by promoting its membrane localization and by abolishing the inhibitory association of calmodulin (2,3). PKA phosphorylates GRK2 at Ser685, which facilitates the association of GRK2 with a beta-adrenergic receptor (4). Erk inhibits GRK2 activity via phosphorylation at Ser670 (5). Src phosphorylates GRK2 at multiple tyrosine residues (Tyr13, 86 and 92), which activates GRK2 activity and promotes GRK2 degradation (6,7).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting

Background: Grp75, also known as mortalin, is a member of Hsp70 family of chaperone proteins that is not heat-inducible (1,2). This protein is essential for transporting many mitochondrial proteins from the cytoplasm to mitochondria (3). Grp75 inactivates the tumor suppressor p53 (4). Studies found that Grp75 is overexpressed in many tumor tissues and immortalized human cell lines, suggesting its role in the tumor formation (5). Grp75 is also implicated in cell aging, as its overexpression appears to prolong the life span of human fibroblasts (6).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Secretory proteins are synthesized on polysomes and translocated into the endoplasmic reticulum (ER). Inside ER, these proteins are often modified by disulfide bond formation, amino-linked glycosylation and folding. The ER contains a pool of molecular chaperones, including Grp94, to help ensure correct protein folding. Grp94 is a glucose-regulated protein (1) with sequence homology to Hsp90 (2). In addition to its role in helping to facilitate folding of a number of secretory proteins to their correct conformation (3), studies suggest that Grp94 derived from cancer cells also induces anti-tumor immune responses in mouse tumor models (4, 5). One way in which Grp94 promotes tumor immunogenicity is its ability to bind to and present tumor-derived peptides as antigens (6). Furthermore, Grp94 has also been shown to induce maturation of dendritic cells (7). Taken together, Grp94 functions both as a tumor-specific antigen and as an activator of antigen-presenting cells to elicit an anti-cancer immune response (8).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Glycogen synthase kinase-3 (GSK-3) was initially identified as an enzyme that regulates glycogen synthesis in response to insulin (1). GSK-3 is a ubiquitously expressed serine/threonine protein kinase that phosphorylates and inactivates glycogen synthase. GSK-3 is a critical downstream element of the PI3K/Akt cell survival pathway whose activity can be inhibited by Akt-mediated phosphorylation at Ser21 of GSK-3α and Ser9 of GSK-3β (2,3). GSK-3 has been implicated in the regulation of cell fate in Dictyostelium and is a component of the Wnt signaling pathway required for Drosophila, Xenopus, and mammalian development (4). GSK-3 has been shown to regulate cyclin D1 proteolysis and subcellular localization (5).

$260
100 µl
APPLICATIONS
REACTIVITY
All Species Expected

Application Methods: Western Blotting

Background: Epitope tags are useful for the labeling and detection of proteins using immunoblotting, immunoprecipitation, and immunostaining techniques. Because of their small size, they are unlikely to affect the tagged protein’s biochemical properties.

$260
100 µl
APPLICATIONS

Application Methods: Immunoprecipitation, Western Blotting

Background: Epitope tags are useful for the labeling and detection of proteins using immunoblotting, immunoprecipitation, and immunostaining techniques. Because of their small size, they are unlikely to affect the tagged protein’s biochemical properties.

$260
100 µl
APPLICATIONS
REACTIVITY
Bovine, Human, Monkey, Mouse, Rat

Application Methods: Immunohistochemistry (Paraffin), Immunoprecipitation, Western Blotting

Background: Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines, and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines, and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines, and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Heterotrimeric guanine nucleotide-binding proteins (G proteins) consist of α, β and γ subunits and mediate the effects of hormones, neurotransmitters, chemokines, and sensory stimuli. To date, over 20 known Gα subunits have been classified into four families, Gα(s), Gα(i/o), Gα(q) and Gα(12), based on structural and functional similarities (1,2). Phosphorylation of Tyr356 of Gα(q)/Gα(11) is essential for activation of the G protein, since phenylalanine substitution for Tyr356 changes the interaction of Gα with receptors and abolishes ligand-induced IP3 formation (3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey

Application Methods: Immunohistochemistry (Paraffin), Western Blotting

Background: Cell growth is a fundamental biological process whereby cells accumulate mass and increase in size. The mammalian Target of Rapamycin (mTOR) pathway regulates growth by coordinating energy and nutrient signals with growth factor-derived signals (1). mTOR is a large protein kinase with two different complexes. One complex contains mTOR, GβL, and raptor, which is a target of rapamycin. The other complex, insensitive to rapamycin, includes mTOR, GβL, and rictor (1). GβL associates with the kinase domain of mTOR and stimulates mTOR kinase activity (2). A reduction in GβL expression has been shown to decrease in vivo phosphorylation of S6K1 (2).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Immunoprecipitation, Western Blotting

Background: Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that causes symptoms including hamartomas in brain, kidney, heart, lung and skin (1). The tumor suppressor genes TSC1 and TSC2 encode hamartin and tuberin, respectively (2,3). Hamartin and tuberin form a functional complex and are involved in numerous cellular activities such as vesicular trafficking, regulation of the G1 phase of the cell cycle, steroid hormone regulation, Rho activation and anchoring neuronal intermediate filaments to the actin cytoskeleton (4-9). The combination of genetic, biochemical and cell-biological studies demonstrate that the tuberin/hamartin complex functions as a GTPase-activating protein for the Ras-related small G protein Rheb and thus inhibits targets of rapamycin including mTOR. Cells lacking hamartin or tuberin fail to inhibit phosphorylation of S6 kinase resulting in the activation of S6 ribosomal protein's translation of 5'TOP mRNA transcripts (10). Hamartin is phosphorylated by CDK1 (cdc2) at Thr417, Ser584 and Thr1047 in cells in G2/M phase of the cell cycle (11).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Ubiquitinating enzymes (UBEs) catalyze protein ubiquitination, a reversible process countered by deubiquitinating enzyme (DUB) action (1,2). Five DUB subfamilies are recognized, including the USP, UCH, OTU, MJD and JAMM enzymes. Herpesvirus-associated ubiquitin-specific protease (HAUSP, USP7) is an important deubiquitinase belonging to USP subfamily. A key HAUSP function is to bind and deubiquitinate the p53 transcription factor and an associated regulator protein Mdm2, thereby stabilizing both proteins (3,4). In addition to regulating essential components of the p53 pathway, HAUSP also modifies other ubiquitinylated proteins such as members of the FoxO family of forkhead transcription factors and the mitotic stress checkpoint protein CHFR (5,6).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Immunoprecipitation, Western Blotting

Background: Host cell factor C1 (HCFC1) was first identified as the host cell factor for human herpes simplex virus infection. HCFC1 and the viral protein VP16 belong to a multi-protein complex that promotes transcription of viral immediate early genes (1). The relatively large HCFC1 protein contains 6 centrally located 26 amino acid repeats that can be O-GlcNAcylated and subjected to O-linked beta-N-acetylglucosamine transferase (OGT) cleavage (2-4). The resulting amino-terminal (HCFC1-N) and carboxy-terminal (HCFC1-C) fragments are non-covalently associated and play important roles in cell cycle regulation. The HCFC1-N peptide facilitates progression through the G1 phase of the cell cycle while HCFC1-C enables proper mitosis and cytokinesis during the M phase (5-7). As HCFC1 plays an important role in neurodevelopment, mutations in the corresponding gene are associated with neurodevelopmental disorders (e.g., intellectual disability) in humans (8).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Immunoprecipitation, Western Blotting

Background: Host cell factor C1 (HCFC1) was first identified as the host cell factor for human herpes simplex virus infection. HCFC1 and the viral protein VP16 belong to a multi-protein complex that promotes transcription of viral immediate early genes (1). The relatively large HCFC1 protein contains 6 centrally located 26 amino acid repeats that can be O-GlcNAcylated and subjected to O-linked beta-N-acetylglucosamine transferase (OGT) cleavage (2-4). The resulting amino-terminal (HCFC1-N) and carboxy-terminal (HCFC1-C) fragments are non-covalently associated and play important roles in cell cycle regulation. The HCFC1-N peptide facilitates progression through the G1 phase of the cell cycle while HCFC1-C enables proper mitosis and cytokinesis during the M phase (5-7). As HCFC1 plays an important role in neurodevelopment, mutations in the corresponding gene are associated with neurodevelopmental disorders (e.g., intellectual disability) in humans (8).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse

Application Methods: Immunoprecipitation, Western Blotting

Background: Acetylation of the histone tail causes chromatin to adopt an "open" conformation, allowing increased accessibility of transcription factors to DNA. The identification of histone acetyltransferases (HATs) and their large multiprotein complexes has yielded important insights into how these enzymes regulate transcription (1,2). HAT complexes interact with sequence-specific activator proteins to target specific genes. In addition to histones, HATs can acetylate nonhistone proteins, suggesting multiple roles for these enzymes (3). In contrast, histone deacetylation promotes a "closed" chromatin conformation and typically leads to repression of gene activity (4). Mammalian histone deacetylases can be divided into three classes on the basis of their similarity to various yeast deacetylases (5). Class I proteins (HDACs 1, 2, 3, and 8) are related to the yeast Rpd3-like proteins, those in class II (HDACs 4, 5, 6, 7, 9, and 10) are related to yeast Hda1-like proteins, and class III proteins are related to the yeast protein Sir2. Inhibitors of HDAC activity are now being explored as potential therapeutic cancer agents (6,7).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting

Background: Acetylation of the histone tail causes chromatin to adopt an "open" conformation, allowing increased accessibility of transcription factors to DNA. The identification of histone acetyltransferases (HATs) and their large multiprotein complexes has yielded important insights into how these enzymes regulate transcription (1,2). HAT complexes interact with sequence-specific activator proteins to target specific genes. In addition to histones, HATs can acetylate nonhistone proteins, suggesting multiple roles for these enzymes (3). In contrast, histone deacetylation promotes a "closed" chromatin conformation and typically leads to repression of gene activity (4). Mammalian histone deacetylases can be divided into three classes on the basis of their similarity to various yeast deacetylases (5). Class I proteins (HDACs 1, 2, 3, and 8) are related to the yeast Rpd3-like proteins, those in class II (HDACs 4, 5, 6, 7, 9, and 10) are related to yeast Hda1-like proteins, and class III proteins are related to the yeast protein Sir2. Inhibitors of HDAC activity are now being explored as potential therapeutic cancer agents (6,7).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse

Application Methods: Western Blotting

Background: HELLS, or LSH1, is a lymphoid-specific helicase thought to be involved in cellular proliferation and leukemogenesis (1,2). It is believed to be a chromatin remodeler and is required for DNMT1-mediated methylation maintenance and DNMT3A/DNMT3B-mediated de novo methylation. The role of HELLS in methylation maintenance was thought to be largely confined to repetitive DNA sequences, including major and minor satellite sequences, rather than single copy genes (3,4); recent evidence suggests a role in genome-wide cysteine methylation at non-repeat sequences (5). De novo methylation maintenance is associated with silencing of specific genes, some known to be involved in pluripotency and lineage commitment (6,7).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse

Application Methods: Western Blotting

Background: The ErbB2 (HER2) proto-oncogene encodes a 185 kDa transmembrane, receptor-like glycoprotein with intrinsic tyrosine kinase activity (1). While ErbB2 lacks an identified ligand, ErbB2 kinase activity can be activated in the absence of a ligand when overexpressed and through heteromeric associations with other ErbB family members (2). Amplification of the ErbB2 gene and overexpression of its product are detected in almost 40% of human breast cancers (3). Binding of the c-Cbl ubiquitin ligase to ErbB2 at Tyr1112 leads to ErbB2 poly-ubiquitination and enhances degradation of this kinase (4). ErbB2 is a key therapeutic target in the treatment of breast cancer and other carcinomas and targeting the regulation of ErbB2 degradation by the c-Cbl-regulated proteolytic pathway is one potential therapeutic strategy. Phosphorylation of the kinase domain residue Tyr877 of ErbB2 (homologous to Tyr416 of pp60c-Src) may be involved in regulating ErbB2 biological activity. The major autophosphorylation sites in ErbB2 are Tyr1248 and Tyr1221/1222; phosphorylation of these sites couples ErbB2 to the Ras-Raf-MAP kinase signal transduction pathway (1,5).