Crystal structure of a myotoxic Asp49-phospholipase A(2) with low catalytic activity: Insights into Ca2+ -independent catalytic mechanism

Correa, Luiz C. [UNESP]Marchi-Salvador, Daniela P. [UNESP]Cintra, Adelia C. O.Sampaio, Suely V.Soares, Andreimar A.Fontes, Marcos R. M. [UNESP]2014-05-202014-05-202008-04-01Biochimica Et Biophysica Acta-proteins and Proteomics. Amsterdam: Elsevier B.V., v. 1784, n. 4, p. 591-599, 2008.1570-9639http://hdl.handle.net/11449/17680A myotoxic Asp49-phospholipase A(2) (Asp49-PLA(2)) with low catalytic activity (BthTX-II from Bothrops jararacussu venom) was crystallized and the molecular-replacement solution has been obtained with a dimer in the asymmetric unit. The quaternary structure of BthTX-II resembles the myotoxic Asp49-PLA2 PrTX-III (piratoxin III from B. pirajai venom) and all non-catalytic and myotoxic dimeric Lys49-PLA(2)s. Despite of this, BthTX-II is different from the highly catalytic and non-myotoxic BthA-I (acidic PLA(2) from B. jararacussu) and other Asp49-PLA(2)s. BthTX-II structure showed a severe distortion of calcium-binding loop leading to displacement of the C-terminal region. Tyr28 side chain, present in this region, is in an opposite position in relation to the same residue in the catalytic activity Asp49-PLA(2)s, making a hydrogen bond with the atom 0 delta 2 of the catalytically active Asp49, which should coordinate the calcium. This high distortion may also be confirmed by the inability of BthTX-II to bind Na+ ions at the Ca2+-binding loop, despite of the crystallization to have occurred in the presence of this ion. In contrast, other Asp49-PLA(2)s which are able to bind Ca2+ ions are also able to bind Na+ ions at this loop. The comparison with other catalytic, non-catalytic and inhibited PLA(2)s indicates that the BthTX-II is not able to bind calcium ions; consequently, we suggest that its low catalytic function is based on an alternative way compared with other PLA(2)s. (c) 2008 Elsevier B.V All rights reserved.591-599engphospholipase A(2)Bothrops jararacussu venommyotoxicCa2+-independent enzymatic activityX-ray crystallographyCrystal structure of a myotoxic Asp49-phospholipase A(2) with low catalytic activity: Insights into Ca2+ -independent catalytic mechanismArtigo10.1016/j.bbapap.2008.01.007WOS:000254893400003Acesso restrito