| Popis: |
Neutrophils possess a multicomponent NADPH oxidase system capable of producing large quantities of superoxide in a process known as the respiratory burst (1). Upon stimulation of a phagocytic cell, two cytosolic components of the oxidase, p67(phox) and p47(phax), associate with a membrane-bound flavocytochrome b and a small GTP-binding protein to form a functional enzyme complex. Each of the Phox proteins contains two src homology 3 (SH3) domains, which are of unknown function but are potential mediators of protein-protein interactions between components of the activated oxidase. We have isolated a 47-kDa protein from lysates of differentiated HL60 cells that specifically bound to the carboxyl-terminal SH3 domain of p67(phox) and not to any other SH3 domain tested. This protein was identified as p47(phox), and the putative SH3 domain binding site was located to a carboxyl terminal proline-rich region. Proline-rich synthetic peptides based on this carboxyl-terminal region specifically inhibited the binding of p47(phox) to the carboxyl-terminal SH3 domain of p67(phox), and sequential truncation defined a unique minimal sequence, which, although similar, does not match the consensus sequence defined for other SH3-binding proteins. |
