Roll Out the Half Barrel

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Science  01 Sep 2000:
Vol. 289, Issue 5484, pp. 1429
DOI: 10.1126/science.289.5484.1429g

The existence of similar domains in multidomain proteins indicates that they have evolved through gene duplication and fusion. Now Lang et al (p. 1546; see the Perspective by Miles and Davies) show that the single-domain β/α barrel likely evolved by duplication and fusion of the gene of a half-barrel ancestor. They determined the structures of two enzymes in the histidine biosynthesis pathway, HisA and HisF, at resolutions of 1.85 and 1.45 angstroms, respectively. Structural and sequence analysis strongly suggest that these two eightfold β/α barrels evolved from a common half-barrel ancestor. They suggest that an initial gene duplication would give two half-barrels that are then fused and adapted into an ancestral β/α barrel. A second gene duplication could lead to diversification into two enzymes with distinct catalytic activities.

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