Enables SH3 domain binding activity and non-membrane spanning protein tyrosine kinase activity. Involved in several processes, including immune response-regulating signaling pathway; immune system development; and regulation of signal transduction. Acts upstream of or within several processes, including B cell receptor signaling pathway; peptidyl-tyrosine phosphorylation; and regulation of release of sequestered calcium ion into cytosol. Located in several cellular components, including membrane raft; nucleus; and plasma membrane. Part of protein-containing complex. Is expressed in several structures, including alimentary system; genitourinary system; hemolymphoid system gland; liver and biliary system; and nervous system. Used to study systemic lupus erythematosus. Orthologous to human LYN (LYN proto-oncogene, Src family tyrosine kinase). [provided by Alliance of Genome Resources, Apr 2022]