The three-dimensional structure of narbonin, a seed protein from Vicia narbonensis L, has been determined at 1.8 A resolution. Phase information was obtained by multiple isomorphous replacement and optimized anomalous dispersion. The narbonin structure was initially traced with only 17% amino-acid sequence information and preliminarily refined to a crystallographic R-factor of 16 ...
The three-dimensional structure of narbonin, a seed protein from Vicia narbonensis L, has been determined at 1.8 A resolution. Phase information was obtained by multiple isomorphous replacement and optimized anomalous dispersion. The narbonin structure was initially traced with only 17% amino-acid sequence information and preliminarily refined to a crystallographic R-factor of 16.5%. It is now refined to 15.9% using full sequence information derived from cDNA and after the addition of more solvent molecules. The monomeric molecule of narbonin is an eight-stranded parallel beta-barrel surrounded by alpha-helices in a beta/alpha-topology similar to that first observed in triose phosphate isomerase. Differences exist in the N-terminal part of the polypeptide chain, where the first helix is replaced by a loop and the second beta-strand is followed by an additional antiparallel alpha-sheet placed parallel on top of alpha-helices alpha3 and alpha4. Two short additional secondary structures are present. The first, an alpha-helix, is situated between the seventh beta-strand and the following helix, and the second, which is a 3(10) helix, between the eighth strand and the C-terminal helix. The most striking observation is the lack of a known enzymatic function for narbonin, because all TIM-like structures known so far are enzymes.
Related Citations:
A Tim Barrel Protein without Enzymatic Activity? Crystal Structure of Narbonin at 1.8 Angstroms Resolution Hennig, M., Schlesier, B., Dauter, Z., Pfeffer, S., Betzel, C., Hoehne, W.E., Wilson, K.S. (1992) FEBS Lett 306: 80
Narbonin, a 2S Globulin from Vicia Narbonensis L. Crystallization and Preliminary Crystallographic Data Hennig, M., Schlesier, B., Pfeffer, S., Hoehne, W.E. (1990) J Mol Biol 215: 339
Organizational Affiliation:
European Molecular Biology Laboratory, Hamburg, Germany.
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