The crystal structure of the fab fragment of the monoclonal antibody MAK33. Implications for folding and interaction with the chaperone bip.
The Fab fragment of the murine monoclonal antibody, MAK33, directed against human creatine kinase of the muscle-type, was crystallized and the three-dimensional structure was determined to 2.9 A. The antigen-binding surface of MAK33 shows a convex overall shape typical for immunoglobulins binding large antigens. The structure allows us to analyze the environment of cis-prolyl-peptide bonds whose isomerization is of key importance in the folding process. These residues seem to be involved with not only domain stability but also seem to play a role in the association of heavy and light chains, reinforcing the importance of beta-strand recognition in antibody assembly. The structure also allows the localization of segments of primary sequence postulated to represent binding sites for the ER-specific chaperone BiP within the context of the entire Fab fragment. These sequences are found primarily in beta-strands that are necessary for interactions between the individual domains.
Augustine
J G
JG
Dana-Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.
de La Calle
A
A
Knarr
G
G
Buchner
J
J
Frederick
C A
CA
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000276:immunology; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D003402:Creatine Kinase / Q000276:immunology; D018360:Crystallography, X-Ray; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry* / Q000276:immunology; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D011487:Protein Conformation
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D007140:Immunoglobulin Fab Fragments; D018832:Molecular Chaperones; D010446:Peptide Fragments; D003402:Creatine Kinase