The structure of o-bromocarbobenzoxy-glycyl-L-prolyl-L-leucyl-glycyl-L-proline ethyl acetate monohydrate: a substrate of the enzyme, collagenase

Abstract

The crystal and molecular structure of a synthetic oligopeptide, o-bromocarbobenzoxy-glycyl-prolylleucyl-glycyl-proline ethyl acetate monohydrate, has been established by the X-ray diffraction method. The monoclinic crystal belongs to the space group P21 with Z=2. Cell dimensions are a= 13710, b= 14.007, c= 10.861 ~ and fl= 114.60 °. As in the case of p-bromocarbobenzoxy-glycyl-prolyl-leucylglycine(tetrapeptide), the peptide chain is folded back at the Pro(l) and Leu residues to form two intramolecular hydrogen bonds between two glycine residues. This folding conformation (called 'or-Ufolding' in this paper) is almost identical to that in the tetrapeptide. This conformation is found in other oligopeptides and also in some protein structures; hence, it is understood to be one of the specific and stable conformations, in contrast with that proposed for the collagen molecule. In relation to this conformation, the 'fl-U-folding' conformation is also discussed. In the crystal structure, intermolecular hydrogen bonds are observed between the peptide bonds of Pro(1)-Leu residues via the water molecule. The ethyl acetate molecule is in the hydrophobic environments. Generally speaking, intermolecular interaction is weak in this crystal, which is consistent with the lower density of the crystal compared with that of tetrapeptide.