LIME (Lck-interacting molecule) is a 30 kDa double-palmitoylated protein with unusually basic cytoplasmic domain, expressed by T cells. After ligation of CD4 or CD8 T cell coreceptors, LIME is phosphorylated by Src-family kinases and associates with Lck and Fyn kinases and with their negative regulator Csk. Interestingly, Csk-mediated phosphorylation of C-terminal negative-regulatory tyrosine of LIME-associated Lck can result in increase of enzymatic activity compared with the total pool of Lck, thus, LIME serves as a positive regulator of TCR-dependent T cell signaling. However, under some circumstances, LIME may mediate inhibitory signals.