Sequence similarities in (alpha/beta)8-barrel enzymes revealed by conserved regions of alpha-amylase.

The parallel (alpha/beta)8-barrel is a frequently occurring protein-folding motif. Although the arrangement of secondary structural elements along the barrel is very similar in different (alpha/beta)8-barrel enzymes, there is a very low mutual amino acid sequence homology among the enzymes, contributing in part to the hazy view of their evolution. Here an approach to identifying at least the rough of evolutionarily conserved (alpha/beta)8-barrel sequence is presented. Based on the idea that highly conserved sequence regions of a particular enzyme should be more or less conserved in the sequences of the other evolutionary related enzymes, five sequence similarities of ten different (alpha/beta)8-barrel enzymes were revealed, using the five conserved regions of the amino acid sequence of the alpha-amylase (alpha/beta)8-barrel as the templates.