Contiguous binding of decylsulfate on the interface-binding surface of pancreatic phospholipase A2
2008 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 47, no 9, 2899-2907 p.Article in journal (Refereed) Published
Pig pancreatic IB phospholipase A(2) (PLA2) forms three distinguishable premicellar E-i(#) (i = 1, 2, and 3) complexes at successively higher decylsulfate concentrations. The Hill coefficient for E-1(#) is n(1) = 1.6, and n(2) and n(3) for E-2(#) and E-3(#) are about 8 each. Saturation-transfer difference nuclear magnetic resonance (NMR) and other complementary results with PLA2 show that decylsulfate molecules in E-2(#) and E-3(#) are contiguously and cooperatively clustered on the interface-binding surface or i-face that makes contact with the substrate interface. In these complexes, the saturation-transfer difference NMR signatures of H-1 in decylsulfate are different. The decylsulfate epitope for the successive E, complexes increasingly resembles the micellar complex formed by the binding of PLA2 to preformed micelles. Contiguous cooperative amphiphile binding is predominantly driven by the hydrophobic effect with a modest electrostatic shielding of the sulfate head group in contact with PLA2. The formation of the complexes is also associated with structural change in the enzyme. Calcium affinity of E-2(#) appears to be modestly lower than that of the free enzyme and Ell. Binding of decylsulfate to the i-face does not require the catalytic calcium required for the substrate binding to the active site and for the chemical step. These results show that E-i(#) complexes are useful to structurally characterize the cooperative sequential and contiguous binding of amphiphiles on the i-face. We suggest that the allosteric changes associated with the formation of discrete E-i(#) complexes are surrogates for the catalytic and allosteric states of the interface activated PLA2.
Place, publisher, year, edition, pages
ACS , 2008. Vol. 47, no 9, 2899-2907 p.
Biochemistry and Molecular Biology
IdentifiersURN: urn:nbn:se:uu:diva-112411DOI: 10.1021/bi702164nISI: 000253461000023OAI: oai:DiVA.org:uu-112411DiVA: diva2:286169