title: Active site mutants of human secreted Group IIA Phospholipase A2 lacking hydrolytic activity retain their bactericidal effect.
abstract: The Human Secreted Group IIA Phospholipase A(2) (hsPLA2GIIA) presents potent bactericidal activity, and is considered to contribute to the acute-phase immune response. Hydrolysis of inner membrane phospholipids is suggested to underlie the bactericidal activity, and we have evaluated this proposal by comparing catalytic activity with bactericidal and liposome membrane damaging effects of the G30S, H48Q and D49K hsPLA2GIIA mutants. All mutants showed severely impaired hydrolytic activities against mixed DOPC:DOPG liposome membranes, however the bactericidal effect against Micrococcus luteus was less affected, with 50% killing at concentrations of 1, 3, 7 and 9 μg/mL for the wild-type, D49K, H48Q and G30S mutants respectively. Furthermore, all proteins showed Ca(2+)-independent damaging activity against liposome membranes demonstrating that in addition to the hydrolysis-dependent membrane damage, the hsPLA2GIIA presents a mechanism for permeabilization of phospholipid bilayers that is independent of catalytic activity, which may play a role in the bactericidal function of the protein.
authors: Department of Biochemistry and Immunology, FMRP-USP, Universidade de São Paulo, Ribeirão Preto-SP, Brazil.
authors: Lucimara
authors: L
authors: Chioato
authors: Elisangela Aparecida
authors: EA
authors: Aragão
authors: Tatiana Lopes
authors: TL
authors: Ferreira
authors: Richard J
authors: RJ
authors: Ward
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D001483:Base Sequence; D055162:Biocatalysis; D020134:Catalytic Domain; D017931:DNA Primers; D054501:Group II Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008081:Liposomes; D016297:Mutagenesis, Site-Directed; D059748:Proteolysis; D013056:Spectrophotometry, Ultraviolet
chemical_list: D017931:DNA Primers; D008081:Liposomes; D054501:Group II Phospholipases A2