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Effects of amino acids and chirality for molecular folding of desoxazoline‐ascidiacyclamide derivatives: X‐ray crystal structures of four cyclic octapeptides including unusual amino acids, cyclo (–Ile– a Thr– D ‐Val–Thz–) 2 , cyclo (–Ala– a Thr– D ‐Val–Thz–Ile– a Thr– D ‐Val–Thz–), cyclo (–Val– a Thr– D ‐Val–Thz–Ile– a Thr– D ‐Val–Thz–), and cyclo (–Ile– a Thr–Val–Thz–Ile– a Thr– D ‐Val–Thz–)
Author(s) -
Asano Akiko,
Doi Mitsunobu,
Kobayashi Kiyomi,
Arimoto Masao,
Ishida Toshimasa,
Katsuya Yoshio,
Mezaki Yoshihiro,
Hasegawa Hiroshi,
Nakai Masamichi,
Sasaki Masahiro,
Taniguchi Taizo,
Terashima Akira
Publication year - 2001
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(200103)58:3<295::aid-bip1006>3.0.co;2-x
Subject(s) - chemistry , chirality (physics) , stereochemistry , residue (chemistry) , peptide , folding (dsp implementation) , crystal structure , molecule , crystallography , cyclic peptide , amino acid , peptide conformation , chiral symmetry , organic chemistry , biochemistry , physics , engineering , quantum mechanics , nambu–jona lasinio model , electrical engineering , quark
Desoxazoline derivative of ascidiacyclamide ( 1 ), cyclo (– L ‐Ile– L ‐ allo ‐threonine– D ‐Val–thiazole–) 2 , was modified to disturb the C 2 ‐symmetry. An Ile 1 residue of 1 was replaced for Ala ( 2 ) or Val ( 3 ), and the D ‐Val 3 residue was replaced for Val ( 4 ). The crystal structures of 1 – 4 were analyzed by x‐ray diffraction methods. The molecules of all compounds were folded and this type of structure was not observed in x‐ray structures of ascidiacyclamide derivatives so far except for patellamide D. The folding patterns of 1 – 4 were similar to each other and resembled that of patellamide. The asymmetric modifications at position 1 caused the conformational changes at local area, and these were related with the peptide–peptide and peptide–solvent interactions. Despite the diverse backbone conformation by the epimeric modification at position 3, the entire molecule of 4 was folded. These results mean that (1) the desoxazoline‐ascidiacyclamides favored the folded structures and (2) the modifications of the side chain size at position 1 and the chirality at position 3 brought the local conformational changes to derivatives, suggesting that (3) the lack of the oxazoline block leads to conformational flexibility of 1 – 4 , which accepts the conformational change with no drastic change on the entire structure. © 2001 John Wiley & Sons, Inc. Biopolymers 58: 295–304, 2001