Structures of the complexes of a potent anti-HIV protein cyanovirin-N and high mannose oligosaccharides.
The development of anti-human immunodeficiency virus (HIV) microbicides for either topical or ex vivo use is of considerable interest, mainly due to the difficulties in creating a vaccine that would be active against multiple clades of HIV. Cyanovirin-N (CV-N), an 11-kDa protein from the cyanobacterium (blue-green algae) Nostoc ellipsosporum with potent virucidal activity, was identified in the search for such antiviral agents. The binding of CV-N to the heavily glycosylated HIV envelope protein gp120 is carbohydrate-dependent. Since previous CV-N-dimannose structures could not fully explain CV-N-oligomannose binding, we determined the crystal structures of recombinant CV-N complexed to Man-9 and a synthetic hexamannoside, at 2.5- and 2.4-A resolution, respectively. CV-N is a three-dimensional domain-swapped dimer in the crystal structures with two primary sites near the hinge region and two secondary sites on the opposite ends of the dimer. The binding interface is constituted of three stacked alpha1-->2-linked mannose rings for Man-9 and two stacked mannose rings for hexamannoside with the rest of the saccharide molecules pointing to the solution. These structures show unequivocally the binding geometry of high mannose sugars to CV-N, permitting a better understanding of carbohydrate binding to this potential new lead for the design of drugs against AIDS.
Macromolecular Crystallography Laboratory, National Cancer Institute/National Institutes of Health, MCL Building 536, Frederick, MD 21702-1201, USA.
Istvan
I
Botos
Barry R
BR
O'Keefe
Shilpa R
SR
Shenoy
Laura K
LK
Cartner
Daniel M
DM
Ratner
Peter H
PH
Seeberger
Michael R
MR
Boyd
Alexander
A
Wlodawer
D019380:Anti-HIV Agents / Q000737:chemistry*; D001426:Bacterial Proteins; D001665:Binding Sites; D002240:Carbohydrate Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D003460:Crystallization; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000378:metabolism; D008358:Mannose / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry*; D011487:Protein Conformation
D019380:Anti-HIV Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D015699:HIV Envelope Protein gp120; D009844:Oligosaccharides; C107733:cyanovirin N; D008358:Mannose