Crystal structure of the complex of a catalytic antibody Fab fragment with a transition state analog: structural similarities in esterase-like catalytic antibodies.
The x-ray structure of the complex of a catalytic antibody Fab fragment with a phosphonate transition-state analog has been determined. The antibody (CNJ206) catalyzes the hydrolysis of p-nitrophenyl esters with significant rate enhancement and substrate specificity. Comparison of this structure with that of the uncomplexed Fab fragment suggests hapten-induced conformational changes: the shape of the combining site changes from a shallow groove in the uncomplexed Fab to a deep pocket where the hapten is buried. Three hydrogen-bond donors appear to stabilize the charged phosphonate group of the hapten: two NH groups of the heavy (H) chain complementarity-determining region 3 (H3 CDR) polypeptide chain and the side-chain of histidine-H35 in the H chain (His-H35) in the H1 CDR. The combining site shows striking structural similarities to that of antibody 17E8, which also has esterase activity. Both catalytic antibody ("abzyme") structures suggest that oxyanion stabilization plays a significant role in their rate acceleration. Additional catalytic groups that improve efficiency are not necessarily induced by the eliciting hapten; these groups may occur because of the variability in the combining sites of different monoclonal antibodies that bind to the same hapten.
Laboratoire de Biologie Structurale, Centre National de la Recherche Scientifique, Université Paris Sud, Gif-sur-Yvette, France.
J B
JB
Charbonnier
E
E
Carpenter
B
B
Gigant
B
B
Golinelli-Pimpaneau
Z
Z
Eshhar
B S
BS
Green
M
M
Knossow
D017151:Antibodies, Catalytic / Q000737:chemistry* / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D003198:Computer Simulation; D003461:Crystallography; D004950:Esterases / Q000737:chemistry* / Q000378:metabolism; D006241:Haptens / Q000737:chemistry / Q000378:metabolism; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009596:Nitrophenols / Q000737:chemistry / Q000276:immunology; D011487:Protein Conformation; D013379:Substrate Specificity; D017356:Synchrotrons
D017151:Antibodies, Catalytic; D000911:Antibodies, Monoclonal; D006241:Haptens; D007140:Immunoglobulin Fab Fragments; D009596:Nitrophenols; D004950:Esterases; C024836:4-nitrophenol