1nar: Difference between revisions

[[Image:1nar.gif|left|200px]]<br /><applet load="1nar" size="350" color="white" frame="true" align="right" spinBox="true"  

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.

1NAR is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Vicia_narbonensis Vicia narbonensis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NAR OCA].  

[[Category: Wilson, K S.]]

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