Structure–specificity relationships in Abp, a GH27 β-L-arabinopyranosidase from Geobacillus stearothermophilus T6

The three-dimensional structure of the GH27 arabinopyranosidase (Abp) from G. stearothermophilus T6 has been determined by molecular replacement, leading to full structural analysis of wild-type Abp (at 2.28 Å resolution) and its catalytic mutant Abp-D197A with (at 2.20 Å resolution) and without (at 2.30 Å resolution) a bound L-arabinose product. The structures demonstrate that Abp is a tetramer built of two pincer-like dimers, as also confirmed by SAXS.