期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：16
页码：5107-5110
DOI：10.1073/pnas.79.16.5107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The structure of the NH2-terminal, 20-residue membrane-bound portion of melittin has been computed with empirical energies (ECEPP, Empirical Conformational Energy Program for Peptides). First, a search was made for long stretches of nonpolar residues. Then, the low-energy conformations of these segments were built up by combining successively the low-energy conformations of their component di- and tripeptides. The minimum-energy conformations of each of these component peptides used in this buildup process were selected so that each had a distinct backbone conformation; these distinct backbone conformations were designated as nondegenerate minima. Structured segments (i.e., those with only a few low-energy conformations) resulting from this process were identified and used as nucleation sites for building up larger structures by adding adjacent peptide segments. At each stage, the energy of each structure was minimized. Only two low-energy structures were found, both of which were alpha-helical from Gly-1 to Thr-10 and from Pro-14 to Ile-20. In one of them, the first helix continues through Thr-11-Gly-12; in the other, there is a bend at Thr-11-Gly-12. However, because of compensating changes in the dihedral angles, both structures are very similar. The calculated structures seem to agree well with experimental data.
