1 / 30

Beta structures

Beta structures. An awful lot of barrels. Functionally the most diversily populated group (antibodies, enzymes, transport proteins etc…) Second biggest group of protein domain structures (after a/b ). Common properties. Built up from four to over ten beta strands

star
Download Presentation

Beta structures

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Beta structures An awful lot of barrels...

  2. Functionally the most diversily populated group (antibodies,enzymes, transport proteins etc…) • Second biggest group of protein domain structures (after a/b)

  3. Common properties • Built up from four to over ten beta strands • b strands are arranged in predominantly antiparallel fashion • Usually two beta sheets are formed, which pack each against other, resembling barrel or distorted barrel (=double b sandwich)

  4. Up-and-down barrels • Simplest topology • Similar arrangement to TIM barrels, but without helices and all strands are antiparallel

  5. Retinol-binding protein (rbp) • Retinol binds in the inside of barrel (typical for up-and-down barrels)

  6. Retinol binding site in rbp • Hydrophobic part fits in a hydrophobic pocket • Hydroxyl group exposed to solvent OH

  7. Alterating patterns in amino acid sequence of rbp • Hydrophobic amino acids are facing the core • Polar, charged and a few small hydrophobic are exposed to the solvent

  8. Up-and-down barrels can contain more than 8 strands • Porin monomer from Rhodobacter has 14 b strands

  9. b propeller in neuraminidase • Influenza virus protein, involved in virion release from cells • Tetrameric protein, one monomer consists of 6 up-and down b sheets • Builds a propeller-like structure

  10. Neuraminidase tetramer

  11. Active site in b-propeller proteins • On the top of propeller there are extensive loops • The loops form active site

  12. Greek key motifs in antiparallel b barrels

  13. g-crystallin • Found in lenses of your eyes • Each domain built from 2 greek key motifs • One connection across the barrel between two motifs

  14. Evidence for two gene duplication events in g-crystallin evolution • Two domains have about 40% sequence identity • Two motifs within the domain share 20-30% sequence identity 1. 2. x 2 x 2

  15. Jelly roll b-barrel

  16. Arrangement of b strands in jelly roll barrel

  17. Two Greek key motifs in jelly-roll barrel

  18. AH – CHOO ! Jelly-roll barrel in viruses • Very common in subunits of spherical viruses • Barrel is distorted and with helices instead of some loops • Example: Rhinovirus (common cold, that is)

  19. Comparison of all those b-barrels Up-and-down g-crystallin-like jelly-roll

  20. Yet another barrel – chymotrypsin fold • Present in chymotrypsin and all other serine proteases • Several non-protease proteins also contain similar fold • Six strands form the barrel

  21. Structure of chymotrypsin Domain 1 Domain 2

  22. Beta helix • Two different kinds – two-sheet helix and three-sheet helix • Both represent deviations from idealized structure with a single spiral-like strand

  23. Two sheet beta helix

  24. Sequence pattern in two sheet beta helix X9 X7 U8 U8 X7 • Gly-Gly-X-Gly-X-Asp-X-U-X • X=any amino acid • U=big hydrophobic, often Leu • Ca ions sit in between loops • Motif present in several bacterial proteases X9

  25. Three sheet beta helix Unlike two-sheet beta helices, there are no repetitive sequence patterns

  26. Structure of pectate lyase

  27. Spider silk

  28. Structure of spider silk • All-beta fibrous protein • N- and C-terminal parts are variable • A large, up to 800 residues long central region is made from repeats: -(Ala)8-10-Gly-Gly-X-

  29. Structure of spider silk Made up from beta sheets About 30% of beta sheets form microcrystals The rest of beta shets form a flexible matrix Soluble form of spider silk is a-helical! Beta sheets form upon spinning

  30. Properties of spider silk • 5 times stronger than steel • Very elastic – can be stretched 3-4 times its original size without breaking • Lighter than cotton

More Related