Pt-barrel

The PT-barrel, is a novel protein fold that was discovered in the crystal structure of the prenyltransferase, Orf2 from Streptomyces sp. strain CL190.[1]

Orf2-like Prenyltransferase
Crystal structure of a PT-barrel protein.
Identifiers
SymbolPTase_Orf2
PfamPF11468
InterProIPR020965
SCOPe1zb6 / SUPFAM

Structure

The PT-barrel consists of a closed β-sheet comprising ten anti-parallel β-strands arranged around a central β-barrel core, itself surrounded by a ring of α-helices forming the outer, solvent exposed surface of the barrel.

The secondary connectivity nearly conforms to an (ααββ)5 classification, but is more specifically described using the (ααββ)4-(αββ)−α nomenclature, where helices 6 and 8, both involved in inter-protein contacts in the crystal lattice, display a helical “kink”. The most hydrophobic section of the PT-barrel is the region residing between the outer surface of the cylindrical β-barrel and the belt of surrounding α-helices. Additionally, a number of hydrophobic residues located inside the barrel accommodate the prenyl tail of the Geranyl-diPhosphate (GPP) and GSPP molecules, while the diphosphate or the thio-diphosphate head groups of substrate and substrate analogs, respectively, point toward the “upper”, more polar end of the barrel where a Mg2+ ion is coordinated. Finally, the bottom of the barrel is capped by a short C-terminal helix (α11).

References
  1. Kuzuyama T, Noel JP, Richard SB (June 2005). "Structural basis for the promiscuous biosynthetic prenylation of aromatic natural products". Nature. 435 (7044): 983–7. doi:10.1038/nature03668. PMC 2874460. PMID 15959519.
  • Koehl P (July 2005). "Relaxed specificity in aromatic prenyltransferases". Nat. Chem. Biol. 1 (2): 71–2. doi:10.1038/nchembio0705-71. PMID 16408001.
  • Botta B, Delle Monache G, Menendez P, Boffi A (December 2005). "Novel prenyltransferase enzymes as a tool for flavonoid prenylation". Trends Pharmacol. Sci. 26 (12): 606–8. doi:10.1016/j.tips.2005.09.012. PMID 16229901.

Press Releases

Promiscuous Catalytic Activity Possessed by Novel Enzyme Structure, June 15, 2005
SSRL Science Highlight July 2005
LightSource.org Press Release Number: PR-SSRL-05-3

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