granulysin

Granulysin is a 74-aa basic protein released from human cytolytic T lymphocytes (CTL, Tc) and natural killer cells (NK).

'The five-helical bundle of granulysin resembles other "saposin folds" (such as NK-lysin). Positive charges distribute in a ring around the granulysin molecule, and one face has net positive charge. Sulfate ions bind near the segment of the molecule identified as most membrane-lytic and of highest hydrophobic moment. The ion locations may indicate granulysin's orientation of initial approach towards the membrane. The crystal packing reveals one way to pack a sheet of granulysin molecules at the cell surface for a concerted lysis effort. The energy of binding granulysin charges to the bacterial membrane could drive the subsequent lytic processes. The loosely packed core facilitates a hinge or scissors motion towards exposure of hydrophobic surface that we propose tunnels the granulysin into the fracturing target membrane.'[pm] Granulysin crystal structure and a structure-derived lytic mechanism. Anderson DH, Sawaya MR, Cascio D, Ernst W, Modlin R, Krensky A, Eisenberg D. J Mol Biol. 2003 Jan 10;325(2):355-65.

tags [Proteins] [granulysin] [killer cells] [saposin folds]