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Design of peptides: Crystal and molecular structure of a 310-helical peptide N-Boc-L-Phe-dehydro-Phe-L-Val-L-Phe-dehydro-Phe-L-Val-Och3

✍ Scribed by B. Padmanabhan; T. P. Singh

Publisher
Wiley (John Wiley & Sons)
Year
1993
Tongue
English
Weight
536 KB
Volume
33
Category
Article
ISSN
0006-3525

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✦ Synopsis

Highly specific peptide structures can be designed by inserting dehydro residues into peptide sequences. The peptide N-Boc-L-Phe-dehydro-Phe-L-Val-L-Phe-dehydro-Phe-~-V~-OCH~, synthesized by conventional procedures, crystallizes from methanol-water mixtures at 4°C in the tetragonal space group P43 with cell parameters a = b = 13.829 k 0.003 A, c = 27.587 ? 0.008 A, V = 5275.5 k 0.2 A3, 2 = 4, d, = 1.152 k 0.005 g ~m -~, d,, = 1.150 k 0.005 g ~m -~. The overall residual factor R = 0.084 for 2342 reflections, with 28, , = 140" using CuKa radiation. The backbone torsion angles are 8 ' = -171 (1) ", wo = 168( 1) O , 41 = 77 (2) O , $1 = 41(2)O, ~1 = 169(1)O, 4 2 = -46(2)O, J/2 = -24(2)", ~2 = 179(1)", 43 = -63(2)O, 11.3 = -19(2)O, ~3 = 171(1)", 4 4 = -67(2)O, $4 = -8(1)O, 04 = 169(1)O, 4 5 = -61(1)', $5 = -26( 1 ) ", w5 = 177( 1 ) ", 46 = -122( 1 ) O , +: = 26(2) O .

The peptide adopts a 3,,-helical conformation with three intramolecular hydrogen bonds ( i + 3 + i) involving carbonyl oxygen atoms of Phel, dehydro-Phe2, Va13, and the NH groups of Phe4, dehydro-Phe5, and Val6 with distances of 3.01 ( 1 1, 2.82 ( 1 ) , and 3.09 (2) A, respectively. The structure determination revealed that a hexapeptide with two dehydro-Phe residues at ( i + 2) and ( i + 5) positions generates a 310-helical conformation. The helical peptide molecules are arranged in a major helical arrangement about the 43 axis. These helices are packed parallel to the c axis and form several interdigitating hydrogen bonds. The interhelix hydrogenbonding regions are separated by van der Waals interactions involving the side chains of Phe, dehydro-Phe, and Val residues.

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