2PYS: Crystal Structure Of A Five Site Mutated Cyanovirin-N With A Mannose Dimer Bound At 1.8 A Resolution

Citation:
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.
PDB ID: 2PYSDownload
MMDB ID: 54113
PDB Deposition Date: 2007/5/16
Updated in MMDB: 2007/11
Experimental Method:
x-ray diffraction
Resolution: 1.8  Å
Source Organism:
Similar Structures:
Biological Unit for 2PYS: dimeric; determined by author
Molecular Components in 2PYS
Label Count Molecule
Proteins (2 molecules)
2
Cyanovirin-n
Molecule annotation
Chemicals (4 molecules)
1
4
* Click molecule labels to explore molecular sequence information.

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