Structural and functional importance of theβ-turn in proteins. Studies on proline-containing peptides |
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Authors: | V S Ananthanarayanan S K Attah-poku P L Mukkamala P H Rehse |
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Institution: | (1) Department of Biochemistry, Memorial University of Newfoundland, AIB 3X9 St. John’s, Newfoundland, Canada |
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Abstract: | We report here two sets of results on proline-containing linear peptides, one of which brings out the role of theβ-turn conformation in the structure of nascent collagen while the other points to the functional importance of the β-turn
in calcium-binding proteins. Based on the data on peptides containing the -Pro-Gly-sequence, we had proposed and experimentally
verified that theβ-turn conformation in these peptides is a structural requirement for the enzymic hydroxylation of the proline residues in
the nascent (unhydroxylated) procollagen molecule. Our recent data, presented here, on the conformation of peptides containing
both the -Pro-Gly- and -Gly-Pro-sequences reveal that while theβ-turn in the substrate molecule is required at the catalytic site of prolyl hydroxylase, the polyproline-II structure is necessary
for effective binding at the active site of the enzyme. Thus, peptides containing either theβ-turn or the polyproline-II structure alone are found to act only as inhibitors while those with the polyproline-II followed
byβ-turn serve as substrates of the enzyme. In another study, we have synthesized the two linear peptides: Boc-Pro-D-Ala-Ala-NHCH3 and Boc-Pro-Gly-Ala-NHCH3 each of which adopts, in solution, a structure with two consecutiveβ-turns, as judged from circular dichroism, infrared and nuclear magnetic resonance data. Drastic spectral changes are seen
in these peptides on binding to Ca2+. Both the peptides show a distinct specificity to Ca2+ over Mg2+, Na+ and Li+. A conformational change in the peptides occurs on Ca2+ binding which brings together the carbonyl groups to coordinate with the metal ion. These results imply a functional role
for theβ-turn in Ca2+ — binding proteins. |
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Keywords: | β -Turn proline peptides collagen prolyl hydroxylase calcium-binding proteins protein structure |
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