1w70: Difference between revisions

The neutrophil NADPH oxidase produces superoxide anions in response to, infection. This reaction is activated by association of cytosolic factors, p47phox and p67phox, and a small G protein Rac with the membranous, flavocytochrome b558. Another cytosolic factor, p40phox, is associated to, the complex and is reported to play regulatory roles. Initiation of the, NADPH oxidase activation cascade has been reported as consecutive to, phosphorylation on serines 359/370 and 379 of the p47phox C terminus., These serines surround a polyproline motif that can interact with the Src, homology 3 (SH3) module of p40phox (SH3p40) or the C-terminal SH3 of, p67phox (C-SH3p67). The latter one presents a higher affinity in the, resting state for p47phox. A change in SH3 binding preference following, phosphorylation has been postulated earlier. Here we report the crystal, structures of SH3p40 alone or in complex with a 12-residue proline-rich, region of p47phox at 1.46 angstrom resolution. Using intrinsic tryptophan, fluorescence measurements, we compared the affinity of the strict, polyproline motif and the whole C terminus peptide with both SH3p40 and, C-SH3p67. These data reveal that SH3p40 can interact with a consensus, polyproline motif but also with a noncanonical motif of the p47phox C, terminus. The electrostatic surfaces of both SH3 are very different, and, therefore the binding preference for C-SH3p67 can be attributed to the, polyproline motif recognition and particularly to the Arg-368p47 binding, mode. The noncanonical motif contributes equally to interaction with both, SH3. The influence of serine phosphorylation on residues 359/370 and 379, on the affinity for both SH3 domains has been checked. We conclude that, contrarily to previous suggestions, phosphorylation of Ser-359/370 does, not modify the SH3 binding affinity for both SH3, whereas phosphorylation, of Ser-379 has a destabilizing effect on both interactions. Other, mechanisms than a phosphorylation induced switch between the two SH3 must, therefore take place for NADPH oxidase activation cascade to start.

1W70 is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with SO4, ACE and TFA as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1W70 OCA].  

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