Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
J Struct Biol. 1998;122(1-2):236-46.

Structure and evolution of parallel beta-helix proteins.

Author information

  • 1Institute of Food Research, Reading Laboratory, Earley Gate, Whiteknights Road, Reading, RG6 6BZ, United Kingdom.

Abstract

Three bacterial pectate lyases, a pectin lyase from Aspergillus niger, the structures of rhamnogalacturonase A from Aspergillus aculeatus, RGase A, and the P22-phage tailspike protein, TSP, display the right-handed parallel beta-helix architecture first seen in pectate lyase. The lyases have 7 complete coils while RGase A and TSP have 11 and 12, respectively. Each coil contains three beta-strands and three turn regions named PB1, T1, PB2, T2, PB3, and T3 in their order of occurrence. The lyases have homologous sequences but RGase A and TSP do not show obvious sequence homology either to the lyases or to each other. However, the structural similarities between all these molecules are so extensive that divergence from a common ancestor is much more probable than convergence to the same fold. The region PB2-T2-PB3 is the best conserved region in the lyases and shows the clearest structural similarity. Not only is the pleating and the direction of the hydrogen bonding in the sheets conserved, but so is the unusual alphaL-conformation turn between the two sheets. However, the overall shape, the position of long loops, a conserved alpha-helix that covers the amino-terminal end of the parallel beta-helix and stacks of residues in alphaR-conformation at the start of PB1 all suggest a common ancestor. The functional similarity, that the enzymes all bind alpha-galactose containing polymers at an equivalent site involving PB1 and its two flanking turn regions, further supports divergent evolution. We suggest that the stacking of the coils and the unusual near perpendicular junction of PB2 and PB3 make the parallel beta-helix fold especially likely to maintain similar main chain conformations during divergent evolution even after all vestige of similarity in primary structure has vanished.

Copyright 1998 Academic Press.

PMID:
9724625
[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science
    Loading ...
    Write to the Help Desk