Maintain refrigerated at 2-8°C for up to 6 months. For long term storage store at -20°C in small aliquots to prevent freeze-thaw cycles.

The human T-cell or lymphocyte specific gene Lck/p56 is a member of the Src family of non-receptors tyrosine kinase. Mostly expressed in T cells, Lck has been shown to be critical for the normal development of T lymphocytes (1). Additionally, the N-terminal region of the tyrosine kinase Lck interacts with the cytoplasmic domains of CD4 and CD8 (2). Autophosphorylation at Tyr-394 appears to be required for maximum catalytic activity (3) but it can also be suppressed by phosphorylation of the carboxyl-terminal tyrosine Tyr-505 (4).

A synthetic phospho-peptide corresponding to residues surrounding Tyrosine 505 of human LCK was used as immunogen.

Rabbit

50 mM Tris-Glycine (pH 7.4), 0.15 M NaCl, 40% Glycerol, 0.01% sodium azide and 0.05% BSA.

1. Rudd, CE, et al., Proc. Natl. Acad. Sci., U. S. A. 85, 5190<br>2. Veillette, AM, et al., Cell 55: 301, 1988.<br>3. Boulet, I., Fagard, R., and Fischer, S. Bichem. Biophys. Res. Commun. 149, 56<br>4. Nakamura, K., et al., (1993) Oncogene 8, 3133-3139<br>

Human, Mouse

Tyrosine-protein kinase Lck, Leukocyte C-terminal Src kinase, LSK, Lymphocyte cell-specific protein-tyrosine kinase, Protein YT16, Proto-oncogene Lck, T cell-specific protein-tyrosine kinase, p56-LCK, LCK

WB~~1::1000~10000

Function Non-receptor tyrosine-protein kinase that plays an essential role in the selection and maturation of developing T- cells in the thymus and in the function of mature T-cells. Plays a key role in T-cell antigen receptor (TCR)-linked signal transduction pathways. Constitutively associated with the cytoplasmic portions of the CD4 and CD8 surface receptors. Association of the TCR with a peptide antigen-bound MHC complex facilitates the interaction of CD4 and CD8 with MHC class II and class I molecules, respectively, thereby recruiting the associated LCK protein to the vicinity of the TCR/CD3 complex. LCK then phosphorylates tyrosines residues within the immunoreceptor tyrosine-based activation motifs (ITAM) of the cytoplasmic tails of the TCR-gamma chains and CD3 subunits, initiating the TCR/CD3 signaling pathway. Once stimulated, the TCR recruits the tyrosine kinase ZAP70, that becomes phosphorylated and activated by LCK. Following this, a large number of signaling molecules are recruited, ultimately leading to lymphokine production. LCK also contributes to signaling by other receptor molecules. Associates directly with the cytoplasmic tail of CD2, which leads to hyperphosphorylation and activation of LCK. Also plays a role in the IL2 receptor-linked signaling pathway that controls the T-cell proliferative response. Binding of IL2 to its receptor results in increased activity of LCK. Is expressed at all stages of thymocyte development and is required for the regulation of maturation events that are governed by both pre-TCR and mature alpha beta TCR. Phosphorylates other substrates including RUNX3, PTK2B/PYK2, the microtubule-associated protein MAPT, RHOH or TYROBP. Cellular_Location Cytoplasm. Cell membrane; Lipid-anchor; Cytoplasmic side. Note=Present in lipid rafts in an inactive form Tissue_Location Expressed specifically in lymphoid cells.