LCK (lymphocyte-specific protein tyrosine kinase)

Alias (NCBI)	P56-LCK LSK (T cell-specific protein-tyrosine kinase)
	lck tyrosine kinase (AA 1-142)
	membrane associated protein tyrosine kinase
	proto-oncogene LCK
	protein-tyrosine kinase
	put. ptk (135aa); tyrosine kinase
HGNC (Hugo)	LCK
HGNC Previous name	lymphocyte-specific protein tyrosine kinase
LocusID (NCBI)	3932
Atlas_Id	14
Location	1p35.1  [Link to chromosome band 1p35]
Location_base_pair	Starts at 32251265 and ends at 32286165 bp from pter ( according to hg19-Feb_2009)  [Mapping LCK.png]
	Probe(s) - Courtesy Mariano Rocchi, Resources for Molecular Cytogenetics

Description	DNA sequence is located on chromosome no.1 on the arm 1(p).
Transcription	Consists of 13 exons and 12 introns spanning 12.3 kb.
Pseudogene	Unknown

Description	The kinase p56lck (509 aa) is a T-lymphocyte-specific member of the Src family of non-receptor protein tyrosine kinase. Lck is a 56 kDa phosphoprotein expressed in variety of lymphoid and non-lymphoid cell lineages. Lck contain myristylation sequence, unique amino-terminal regions, followed by Src homology domains SH3 and SH2, a tyrosine kinase catalytic domain, and C-terminal regulatory domain. Lck associates with the inner face of the plasma membrane through its amino-terminus. This interaction is mediated by both myristic acid and palmitic acid that are bound to the amino terminal glycine and Cys-3 and/or Cys-5. The Unique region of Lck represents the domain possessing the greatest sequence diversity within this group of enzymes. This domain is thought to be involved in the interaction of the Lck with specific cellular proteins including Lck substrate. In T-cells it is known, to mediate association with the cytoplasmic tail of T-cell coreceptors CD4 and CD8a. SH3 (Src homology 3) domain is mainly implicated in the regulation of protein-protein interactions, recognizing proline-rich region found in guanine nucleotide exchange factors and GTPase activating proteins. SH2 (Src homology 2) domain of Lck recognizes phosphorylated tyrosine residues on other proteins thereby facilitating the formation of tyrosine phosphorylation-induced multimeric complexes. The tyrosine kinase domain is the catalytic domain of Lck catalyzing the transfer of the gamma-phosphate from ATP to tyrosine residues on proteins. The catalytic domain contains a site of autophosphorylation (Tyr-394), which plays an important role in regulating the protein kinase activity. A C-terminal regulatory domain is also seen containing the major site of tyrosine phosphorylation in vivo (Tyr-505). Phosphorylation of Csk (C-terminal Src kinase) at Tyr-505 leads to inactivation of Lck. Lck is also activated by oxidative stress. Reoxygenation after hypoxia induces Lck kinase activity.
Expression	Expressed in variety of lymphoid and non-lymphoid cell lineages (Breast cancer tissues and other cancers too).
Localisation	Cell membrane
Function	T-cell development, T-cell activation.
Homology	Shares sequence homology with other Src family kinases (Src, Hck, Fyn, Blk, Lyn, Fgr, Yes, and Yrk).

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