Refined molecular and crystal structure of silk I based on Ala–Gly and (Ala–Gly)2—Ser–Gly peptide sequence

✍ Scribed by Kenji Okuyama; R. Somashekar; Keiichi Noguchi; Syuji Ichimura

• Publisher: Wiley (John Wiley & Sons)
• Year: 2001
• Tongue: English
• Weight: 160 KB
• Volume: 59
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/1097-0282(20011015)59:5<310::aid-bip1028>3.0.co;2-5

✦ Synopsis

The molecular and crystal structure of one of the crystalline modifications of Bombyx mori, silk I, was determined by x-ray diffraction method. Cell dimensions are essentially the same as those found in the synthetic model peptide poly(L-Ala-Gly). The (, ) values of L-Ala and Gly in the repeating unit are (Ϫ112°, Ϫ6°), and (71°, Ϫ99°) respectively, which are in the Bridge and the forth quadrant regions of the Ramachandran map, respectively. The observed molecular conformation in the present study has a "crank-shaft" or a S-shaped zigzag arrangement, leading to a remarkable agreement of observed and calculated structure amplitudes for both dipeptide and hexapeptide sequences, and has a reasonable hydrogen bond networks. Obtained (, ) values are quite different from those reported by Lotz and Keith, even though overall appearances are quite similar to each other. In spite of intra-and intermolecular hydrogen-bond networks, silk I structure changes easily to the silk II by a mechanical deformation. This fragility may be due to the above peculiar crank-shaft conformation deduced from the alternating structure of alanine and glycine.