Mizunari H, Kakinuma K, Suzuki K, Namiki H, Kuratsuji T, Tsunawaki S. Nucleoside-triphosphate binding of the two cytosolic components of the respiratory burst oxidase system: evidence for its inhibition by the 2',3'-dialdehyde derivative of NADPH and desensitization in their translocated states.
BIOCHIMICA ET BIOPHYSICA ACTA 1993;
1220:21-30. [PMID:
8268240 DOI:
10.1016/0167-4889(93)90092-4]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Affinity labeling of the two cytosolic components of the respiratory burst oxidase system, p49-phox and p63-phox, from resting porcine neutrophils was carried out with [32P]NADPH dialdehyde (oNADPH), [32P]oGTP and [32P]oATP. p49-phox and p63-phox showed 10-times higher affinities for both oGTP and oATP than for oNADPH, suggesting that they are nucleoside triphosphate (NTP)-binding proteins, rather than the NADPH-binding site of the oxidase. In addition, oNADPH markedly inhibited the affinity labeling of p49-phox with [32P]oGTP and [32P]oATP, well reflecting its inhibitory effect on the oxidase activity in the cell-free system, which was previously reported to propose the NADPH-binding site in a cytosolic component. Stimulation of porcine neutrophils with either myristic acid or phorbol myristate acetate resulted in great enhancement of the oxidase activity, and in considerable translocation of p49-phox and p63-phox. Nevertheless, the affinity labeling of the stimulated cell membranes in both cases revealed no labeled bands corresponding to molecular masses of 49 kDa and 63 kDa. p49-phox derived from the stimulated membranes had lost its [32P]oGTP binding ability in contrast with that from resting cytosol, suggesting that the NTP-binding sites of the two cytosolic components may be desensitized on NTP binding in their translocated states.
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