Abbreviated Journal Title
J. Biol. Chem.
SITE-DIRECTED MUTAGENESIS; BETA-SHEET STRUCTURE; INTERFACIAL ACTIVATION; INFRARED-SPECTROSCOPY; STRUCTURAL-CHANGES; MEMBRANE-BINDING; COILED-COILS; ALPHA-HELIX; AGKISTRODON PISCIVORUS; SECONDARY STRUCTURE; Biochemistry & Molecular Biology
The phospholipase A(2) (PLA(2)) enzymes are activated by binding to phospholipid membranes. Although the N-terminal alpha-helix of group I/II PLA(2)s plays an important role in the productive mode membrane binding of the enzymes, its role in the structural aspects of membrane-induced activation of PLA(2)s is not well understood. In order to elucidate membrane-induced conformational changes in the N-terminal helix and in the rest of the PLA(2), we have created semisynthetic human group IB PLA(2) in which the N-terminal decapeptide is joined with the C-13-labeled fragment, as well as a chimeric protein containing the N-terminal decapeptide from human group IIA PLA(2) joined with a C-13-labeled fragment of group IB PLA(2). Infrared spectral resolution of the unlabeled and C-13-labeled segments suggests that the N-terminal helix of membrane-bound IB PLA(2) has a more rigid structure than the other helices. On the other hand, the overall structure of the chimeric PLA(2) is more rigid than that of the IB PLA(2), but the N-terminal helix is more flexible. A combination of homology modeling and polarized infrared spectroscopy provides the structure of membrane-bound chimeric PLA(2), which demonstrates remarkable similarity but also distinct differences compared with that of IB PLA(2). Correlation is delineated between structural and membrane binding properties of PLA(2)s and their N-terminal helices. Altogether, the data provide evidence that the N-terminal helix of group I/II PLA(2)s acts as a regulatory domain that mediates interfacial activation of these enzymes.
Journal of Biological Chemistry
Qin, Shan; Pande, Abhay H.; Nemec, Kathleen N.; He, Xiaomei; and Tatulian, Suren A., "Evidence for the regulatory role of the N-terminal helix of secretory phospholipase A(2) from studies on native and chimeric proteins" (2005). Faculty Bibliography 2000s. 5559.