Proline kinks in transmembrane alpha-helices.
Integral membrane proteins often contain proline residues in their presumably alpha-helical transmembrane segments. This is in marked contrast to globular proteins, where proline is rarely found inside alpha-helices. Proline residues cause kinks in helices, and, in addition to leaving the i-4 backbone carbonyl without its normal hydrogen bond donor, also sterically prevent the (i-3)-carbonyl-(i + l)-amide backbone hydrogen bond from forming. Here, some structural aspects of proline kinks in transmembrane helices are discussed on the basis of an analysis of Pro-kinked helices in the photosynthetic reaction center and bacteriorhodopsin, as well as results from an analysis of Pro-containing transmembrane segments identified in the NBRF Protein Sequence Databank.
von Heijne
G
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Department of Molecular Biology, Karolinska Institute Center for Biotechnology, Huddinge, Sweden.
D000595:Amino Acid Sequence; D001436:Bacteriorhodopsins / Q000737:chemistry*; D006860:Hydrogen Bonding; D008565:Membrane Proteins / Q000737:chemistry*; D008956:Models, Chemical; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*; D011487:Protein Conformation
D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D001436:Bacteriorhodopsins; D011392:Proline