Roles of aromatic residues in high interfacial activity of Naja naja atra phospholipase A(2)

Citation
M. Sumandea et al., Roles of aromatic residues in high interfacial activity of Naja naja atra phospholipase A(2), BIOCHEM, 38(49), 1999, pp. 16290-16297
Citations number
32
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOCHEMISTRY
ISSN journal
0006-2960 → ACNP
Volume
38
Issue
49
Year of publication
1999
Pages
16290 - 16297
Database
ISI
SICI code
0006-2960(199912)38:49<16290:ROARIH>2.0.ZU;2-N
Abstract
Acidic phospholipase A(2) (PLA(2)) from the venom of Chinese cobra (Naja na ja atra) has high activity on zwitterionic membranes and contains six aroma tic residues, including Tyr-3, Trp-18, Trp-19, Trp-61, Phe-64, and Tyr-110, on its putative interfacial binding surface. To assess the roles of these aromatic residues in the interfacial catalysis of N, n, arm PLA(2), we muta ted them to Ala and measured the effects on its interfacial catalysis. Enzy matic activities of the mutants toward various vesicle substrates and human neutrophils indicate that all but Trp-18 make significant contributions to interfacial catalysis. Among these aromatic residues, Trp-19, Trp-61, and Phe-64 play the most important roles. Binding affinities of the mutants for phospholipid-coated beads and their monolayer penetration indicate that Tr p-19, Trp-61, and Phe-64 are critically involved in interfacial binding of N. n. atra PLA(2) and penetrate into the membrane during the interfacial ca talysis of N. n. atra PLA(2). Further thermodynamic analysis suggests that the side chain of Phe-64 is fully inserted into the hydrophobic core of mem brane whereas these of Trp-19 and Trp-61 are located in the membrane-water interface. Together, these results show that all three types of aromatic re sidues can play important roles in interfacial binding of PLA(2) depending on their location and side-chain orientation. They also indicate that these aromatic side chains interact with membranes in distinct modes because of their different intrinsic preference for different parts of membranes.