The NOXO1β PX Domain Preferentially Targets PtdIns(4,5)P2 and PtdIns(3,4,5)P3

NOX1 beta [NOXO1 (Nox organizer 1) beta] is a cytosolic protein that, in conjunction with NOXA1 (Nox activator 1), regulates generation of reactive oxygen species by the NADPH oxidase 1 (Nox1) enzyme complex. NOX1 beta is targeted to membranes through an N-terminal PX (phox homology) domain. We have used NMR spectroscopy to solve the structure of the NOX1 beta PX domain and surface plasmon resonance (SPR) to assess phospholipid specificity. The solution structure of the NOX1 beta PX domain shows greatest similarity to that of the phosphatidylinositol 3-kinase-C2 alpha PX domain with regard to the positions and types of residues that are predicted to interact with phosphatidylinositol phosphate (PtdInsP) head groups. SPR experiments identify PtdIns(4,5)P-2 and PtdIns(3,4,5)P-3 as preferred targets of NOX1 beta PX. These findings contrast with previous lipid overlay experiments showing strongest binding to monophosphorylated PtdInsP and phosphatidylserine. Our data suggest that localized membrane accumulation of PtdIns(4,5)P-2 or PtdIns(3,4,5)P-2 may serve to recruit NOX1 beta and activate Nox1. (C) 2012 Elsevier Ltd. All rights reserved.