2PYS : Crystal Structure of a Five Site Mutated Cyanovirin-N with a Mannose Dimer Bound at 1.8 A Resolution

Dataset

Description

Experimental Technique/Method:X-RAY DIFFRACTION
Resolution:1.8
Classification:SUGAR BINDING PROTEIN
Release Date:2007-07-31
Deposition Date:2007-05-16
Revision Date:2011-07-13
Molecular Weight:24618.81
Macromolecule Type:Protein
Residue Count:218
Atom Site Count:1585
DOI:10.2210/pdb2pys/pdb

Abstract:
Cyanovirin-N (CV-N) is a 101 amino acid cyanobacterial lectin with potent antiviral activity against HIV, mediated by high-affinity binding to branched N-linked oligomannosides on the viral surface envelope protein gp120. The protein contains two carbohydrate-binding domains, A and B, each of which binds short oligomannosides independently in vitro. The interaction to gp120 could involve either a single domain or both domains simultaneously; it is not clear which mode would elicit the antiviral activity. The model is complicated by the formation of a domain-swapped dimer form, in which part of each domain is exchanged between two monomers, which contains four functional carbohydrate-binding domains. To clarify whether multivalent interactions with gp120 are necessary for the antiviral activity, we engineered a novel mutant, P51G-m4-CVN, in which the binding site on domain A has been knocked out; in addition, a [P51G] mutation prevents the formation of domain-swapped dimers under physiological conditions. Here, we present the crystal structures at 1.8 A of the free and of the dimannose-bound forms of P51G-m4-CVN, revealing a monomeric structure in which only domain B is bound to dimannose. P51G-m4-CVN binds gp120 with an affinity almost 2 orders of magnitude lower than wt CV-N and is completely inactive against HIV. The tight binding to gp120 is recovered in the domain-swapped version of P51G-m4-CVN, prepared under extreme conditions. Our findings show that the presence of at least two oligomannoside-binding sites, either by the presence of intact domains A and B or by formation of domain-swapped dimers, is essential for activity.
Date made availableJul 31 2007
PublisherRCSB-PDB

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