Non-receptor protein tyrosine kinase which is activated following engagement of many different classes of cellular receptors including immune response receptors, integrins and other adhesion receptors, receptor protein tyrosine kinases, G protein-coupled receptors as well as cytokine receptors. Participates in signaling pathways that control a diverse spectrum of biological activities including gene transcription, immune response, cell adhesion, cell cycle progression, apoptosis, migration, and transformation. Due to functional redundancy between members of the SRC kinase family, identification of the specific role of each SRC kinase is very difficult. SRC appears to be one of the primary kinases activated following engagement of receptors and plays a role in the activation of other protein tyrosine kinase (PTK) families. Receptor clustering or dimerization leads to recruitment of SRC to the receptor complexes where it phosphorylates the tyrosine residues within the receptor cytoplasmic domains. Plays an important role in the regulation of cytoskeletal organization through phosphorylation of specific substrates involved in this process (Probable). When cells adhere via focal adhesions to the extracellular matrix, signals are transmitted by integrins into the cell resulting in tyrosine phosphorylation of a number of focal adhesion proteins, including PTK2/FAK1 and paxillin (PXN) (By similarity). Also active at the sites of cell-cell contact adherens junctions and at gap junctions. Implicated in the regulation of pre-mRNA-processing (Probable). Might be involved not only in mediating the transduction of mitogenic signals at the level of the plasma membrane but also in controlling progression through the cell cycle via interaction with regulatory proteins in the nucleus (PubMed:1717492, PubMed:8550628). Involved in anchorage-independent cell growth (PubMed:19307596). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Becomes activated when its major tyrosine phosphorylation site is not phosphorylated. It can also be activated by point mutations as well as by truncations at the C-terminal end or by other mutations. Heme regulates its activity by enhancing the phosphorylation on Tyr-527 (By similarity). Forms a complex with polyoma virus middle T antigen. Interacts with AFAP-110. Interacts with GJA1 and PXN. Localizes to focal adhesion sites following integrin engagement (By similarity). Localization to focal adhesion sites requires myristoylation and the SH3 domain. Expressed to high levels, and with a high degree of kinase activity, in certain fully differentiated cells such as neurons, platelets and macrophages. Isoform 1 is widely expressed. Isoform 2 is expressed only in the muscle. Myristoylated at Gly-2, and this is essential for targeting to membranes. Dephosphorylated at Tyr-527 by PTPRJ. Phosphorylated on Tyr-527 by c-Src kinase (CSK). The phosphorylated form is termed pp60c-src. Dephosphorylated by PTPRJ at Tyr-416. Normally maintained in an inactive conformation with the SH2 domain engaged with Tyr-527, the SH3 domain engaged with the SH2-kinase linker, and Tyr-416 dephosphorylated. Dephosphorylation of Tyr-527 as a result of protein tyrosine phosphatase (PTP) action disrupts the intramolecular interaction between the SH2 domain and Tyr-527, Tyr-416 can then become autophosphorylated, resulting in SRC activation. Phosphorylation of Tyr-527 by CSK allows this interaction to reform, resulting in SRC inactivation (By similarity). S-nitrosylation is important for activation of its kinase activity. Membrane-bound. Belongs to the protein kinase superfamily. Tyr protein kinase family. SRC subfamily.