Protein Engineering, Vol 11, 285-294, Copyright © 1998 by Oxford University Press
RJ Ward, AR Alves, J Ruggiero Neto, RK Arni and G Casari
'SequenceSpace' analysis is a novel approach which has been used to
identify unique amino acids within a sub-family of phospholipases A2 (PLA2)
in which the highly conserved active site residue Asp49 is substituted by
Lys (Lys49-PLA2s). Although Lys49-PLA2s do not bind the catalytic co-factor
Ca2+ and possess extremely low catalytic activity, they demonstrate a
Ca2+-independent membrane damaging activity through a poorly understood
mechanism, which does not involve lipid hydrolysis. Additionally,
Lys49-PLA2s possess combined myotoxic, oedema forming and cardiotoxic
pharmacological activities, however the structural basis of these varied
functions is largely unknown. Using the 'SequenceSpace' analysis we have
identified nine residues highly unique to the Lys49- PLA2 sub-family, which
are grouped in three amino acid clusters in the active site, hydrophobic
substrate binding channel and homodimer interface regions. These three
highly specific residue clusters may have relevance for the
Ca2+-independent membrane damaging activity. Of a further 15 less
stringently conserved residues, nine are located in two additional clusters
which are well isolated from the active site region. The less strictly
conserved clusters have been used in predictive sequence searches to
correlate amino acid patterns in other venom PLA2s with their
pharmacological activities, and motifs for presynaptic and combined
toxicities are proposed.
ARTICLES
A SequenceSpace analysis of Lys49 phopholipases A2: clues towards identification of residues involved in a novel mechanism of membrane damage and in myotoxicity
Department of Physics, IBILCE/UNESP, Sao Jose do Rio Preto-SP, Brazil.
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