Title

Isoform-Specific Membrane Insertion Of Secretory Phospholipase A 2 And Functional Implications

Abstract

Despite increasing evidence that the membrane-binding mode of interfacial enzymes including the depth of membrane insertion is crucial for their function, the membrane insertion of phospholipase A2 (PLA2) enzymes has not been studied systematically. Here, we analyze the membrane insertion of human group IB PLA2 (hIBPLA2) and compare it with that of a structurally homologous V3W mutant of human group IIA PLA2 (V3W-hIIAPLA2) and with a structurally divergent group III bee venom PLA2 (bvPLA2). Increasing the anionic charge of membranes results in a blue shift of the fluorescence of Trp3 of hIBPLA 2, a decrease in quenching by acrylamide, and an increase in enzyme activity, reflecting an enhancement in the membrane binding of PLA2. Fluorescence quenching by brominated lipids indicates significant penetration of Trp3 into fluid POPC/POPG membranes but little insertion into the solid DPPC/DPPG membranes. Increased membrane fluidity also supports hIBPLA 2 activity, suggesting that membrane insertion of hIBPLA2 is controlled by membrane fluidity and is necessary for the full activity of the enzyme. Trp fluorescence quenching of the V3W-hIIAPLA2 and bvPLA2 by water- and membrane-soluble quenchers indicates substantial membrane insertion of Trp3 of V3W-hIIAPLA2, similar to that found for hIBPLA2, and no insertion of tryptophans of bvPLA 2. Our results provide evidence that (a) structurally similar group IB and IIA PLA2s, but not structurally diverse group III PLA 2, significantly penetrate into membranes; (b) membrane insertion is controlled by membrane fluidity and facilitates activation of IB and IIA PLA2s; and (c) structurally distinct PLA2 isoforms may employ different tactics of substrate accession/product release during lipid hydrolysis. © 2006 American Chemical Society.

Publication Date

10-17-2006

Publication Title

Biochemistry

Volume

45

Issue

41

Number of Pages

12436-12447

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1021/bi060898q

Socpus ID

33750087241 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/33750087241

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