1ica
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(New page: 200px<br /><applet load="1ica" size="450" color="white" frame="true" align="right" spinBox="true" caption="1ica" /> '''REFINED THREE-DIMENSIONAL STRUCTURE OF INSEC...)
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Revision as of 15:09, 20 November 2007
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REFINED THREE-DIMENSIONAL STRUCTURE OF INSECT DEFENSIN A
Overview
BACKGROUND: Insect defensin A is a basic 4 kDa protein secreted by Phormia, terranovae larvae in response to bacterial challenges or injuries., Previous biological tests suggest that the bacterial cytoplasmic membrane, is the target of defensin A. The structural study of this protein is the, first step towards establishing a structure-activity relationship and, forms the basis for understanding its antibiotic activity at the molecular, level. RESULTS: We describe a refined model of the three-dimensional, structure of defensin A derived from an extensive analysis of 786, inter-proton nuclear Overhauser effects. The backbone fold involves an, N-terminal loop and an alpha-helical fragment followed by an antiparallel, beta-structure. The helix and the beta-structure are connected by two of, the three disulphide bridges present in defensin A, forming a so-called, 'cysteine-stabilized alpha beta' (CS alpha beta) motif. The N-terminal, loop, which is locally well defined, can occupy different positions with, respect to the other moieties of the molecule. CONCLUSIONS: The CS alpha, beta motif, which forms the core of the defensin A structure, appears to, be a common organization for several families of small proteins with toxic, properties. The distribution of amino acid side chains in the protein, structure creates several hydrophobic or hydrophilic patches. This leads, us to propose that the initial step in the action of positively charged, defensin A molecules with cytoplasmic membranes may involve interactions, with acidic phospholipids.
About this Structure
1ICA is a Single protein structure of sequence from Protophormia terraenovae. Full crystallographic information is available from OCA.
Reference
Refined three-dimensional solution structure of insect defensin A., Cornet B, Bonmatin JM, Hetru C, Hoffmann JA, Ptak M, Vovelle F, Structure. 1995 May 15;3(5):435-48. PMID:7663941
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