Crystal Structures of Repeating Peptides of Elastin. 1. N-tert-Butoxycarbonyl)-L-Valyl-L-Prolyglycyl-L-Valylglycine

The crystal structure of the pentapeptide Boc-Val super(1)-Pro super(2)-Gly super(3)-Val super(4)-Gly super(5)-OH, one of the repeating sequences of tropoelastin, has been determined by the X-ray diffraction method. It crystallizes as a monohydrate in space group P2 sub(1)2 sub(1)2 sub(1) with a = 15.480 (3), b = 21.052 (4), c = 9.387 (2) A and Z = 4. The molecular structure does not have a beta turn as proposed for Boc-Val-Pro-Gly-Val-Gly-OMe in solution but takes a rather extended form at the central part from C' of Pro super(2) to N-H of Gly super(5). The peptice molecules arranged along a 2-fold screw axis ar linked by the hydrogen bonds to make an infinite antiparallel beta sheet.