Crystallization of a novel alpha-amylase, AmyB, from the thermophilic halophile Halothermothrix orenii.

This is a report on the structure determination of AmyB, the second alpha-amylase from Halothermothrix orenii, by X-ray crystallography. This bacterium was isolated from saltpans where conditions consisted of both high temperatures and high NaCl content. AmyB is a 599-residue protein which is stable and significantly active at 358 K in starch solution containing up to 10%(w/v) NaCl. The purified recombinant AmyB protein crystallizes in the monoclinic space group C2, with unit-cell parameters a = 225.85, b = 77.16, c = 50.13 A, beta = 99.32 degrees, using the hanging-drop vapour-diffusion method. The crystal diffracts X-rays to a resolution limit of 1.97 A.