1ib9
From Proteopedia
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SOLUTION STRUCTURE OF MCOTI-II, A MACROCYCLIC TRYPSIN INHIBITOR
Overview
Much interest has been generated by recent reports on the discovery of, circular (i.e. head-to-tail cyclized) proteins in plants. Here we report, the three-dimensional structure of one of the newest such circular, proteins, MCoTI-II, a novel trypsin inhibitor from Momordica, cochinchinensis, a member of the Cucurbitaceae plant family. The structure, consists of a small beta-sheet, several turns, and a cystine knot, arrangement of the three disulfide bonds. Interestingly, the molecular, topology is similar to that of the plant cyclotides (Craik, D. J., Daly, N. L., Bond, T., and Waine, C. (1999) J. Mol. Biol. 294, 1327-1336), which, derive from the Rubiaceae and Violaceae plant families, have antimicrobial, activities, and exemplify the cyclic cystine knot structural motif as part, of their circular backbone. The sequence, biological activity, and plant, family of MCoTI-II are all different from known cyclotides. However, given, the structural similarity, cyclic backbone, and plant origin of MCoTI-II, we propose that MCoTI-II can be classified as a new member of the, cyclotide class of proteins. The expansion of the cyclotides to include, trypsin inhibitory activity and a new plant family highlights the, importance and functional variability of circular proteins and the fact, that they are more common than has previously been believed. Insights into, the possible roles of backbone cyclization have been gained by a, comparison of the structure of MCoTI-II with the homologous acyclic, trypsin inhibitors CMTI-I and EETI-II from the Cucurbitaceae plant family.
About this Structure
1IB9 is a Single protein structure of sequence from Momordica cochinchinensis. Full crystallographic information is available from OCA.
Reference
Circular proteins in plants: solution structure of a novel macrocyclic trypsin inhibitor from Momordica cochinchinensis., Felizmenio-Quimio ME, Daly NL, Craik DJ, J Biol Chem. 2001 Jun 22;276(25):22875-82. Epub 2001 Apr 5. PMID:11292835
Page seeded by OCA on Tue Nov 20 17:14:20 2007
