Structure of the concanavalin A--methyl. cap alpha. -D-mannopyranoside complex at 6-A resolution
The carbohydrate binding site of concanavalin A has been identified in crystals of the concanavalin A-methyl ..cap alpha..-D-mannopyranoside complex and is 35 A from the iodophenol binding site (K. D. Hardman and C. F. Ainsworth (1973), Biochemistry 12, 4442), which has been postulated to be adjacent to the carbohydrate-specific binding site (Edelman et al. (1972), Proc. Natl. Acad. Sci. U.S.A. 69, 2580). The crystals are orthorhombic in space group C222/sub l/ and crystal density measurements indicate a protein mass of four monomers (molecular weight of 104,000) per asymmetric unit. However, the electron density map contains eight monomers/asymmetric unit, revealing lattice disorder. The electron density map with a nominal resolution of 6 A has been solved using three heavy-atom derivatives and the position and orientation of each monomer established. Atomic coordinates of the native protein which has previously been determined (K. D. Hardman (1973), Adv. Exp. Med. Biol. 40, 103) were transposed into this new space group and the gross conformations of the monomers, dimers, and tetramers were found to be very similar to the previous structure. However, some minor differences were apparent even at this resolution. After crystal growth, the methyl ..cap alpha..-D-mannopyranoside was replaced by o-iodophenyl ..beta..-D-glucopyranoside or methyl 2-iodoacetimido-2-deoxy-..cap alpha..-D-glucopyranoside in separate experiments,and difference electron density maps were calculated. The highest peaks for both iodinated sugar derivatives associated with each monomer agreed within a few angstroms of each other and were found near side chains Tyr-12 and -100 and Asp-16 and -208. This region is 10 to 14 A from the manganese, in good agreement with nuclear magnetic resonance (NMR) studies in solution (C. F. Brewer et al. (1973), Biochemistry 12, 4448) and with the site predicted from cross-linked I222 crystal studies (K. D. Hardman (1973), Adv. Exp. Med. Biol. 40, 103). (auth)
- Research Organization:
- Thomas J. Watson Research Center, Yorktown Heights, NY
- OSTI ID:
- 7196860
- Journal Information:
- Biochemistry; (United States), Vol. 15:5
- Country of Publication:
- United States
- Language:
- English
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