Beta trefoil fold

In molecular biology the β trefoil fold is a protein fold that consists of six beta hairpins, each formed by two beta strands. Together these form a beta barrel with a triangular "cap", each consisting of three hairpins. Overall, this structure has an approximate three-fold symmetry.[1][2]

Structure of the beta trefoil fold of Interleukin 1b.

Details

The hairpins are arranged in three β-β-β-loop-β sequences, each having a "Y" or trefoil-like structure. The first and fourth β strands form one hairpin, while the second and third form the other hairpin- each hairpin forms another arm of the "Y" and the long loop forms its trunk.[1][2]

The beta barrel has a 16 Å diameter, and is filled with amino acid side-chains. [1]

Occurrence

Among other proteins, β trefoil fold is found in Kunitz inhibitors of several plants such as soybean, Erythrina caffra and wheat; in members of the interleukin 1 cytokine family (interleukin-1 alpha, interleukin-1 beta and interleukin-1 receptor antagonist); and in fibroblast growth factors 1 and 2.[1][2]

References
  1. Murzin AG, Lesk AM, Chothia C (Jan 1992). "β-trefoil fold: patterns of structure and sequence in the kunitz inhibitors interleukins-1β and 1α and fibroblast growth factors". Journal of Molecular Biology. 223 (2): 531–43. doi:10.1016/0022-2836(92)90668-A. PMID 1738162.
  2. Gosavi S, Whitford PC, Jennings PA, Onuchic JN (Jul 2008). "Extracting function from a β-trefoil folding motif". PNAS. 105 (30): 10384–9. doi:10.1073/pnas.0801343105. PMC 2492465. PMID 18650393.
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