The first successful crystallization of a prokaryotic extremely thermophilic outer surface layer glycoprotein

Methanothermus fervidus belongs to the group of hyperthermophilic Archaea. The Archaea comprise organisms that live under environmental extremes, like high temperature, low pH value or high salt concentration. The outer surfa ce of the pseudomurein sacculi of the cells of Methanothermus fervidus is c overed by glycoprotein subunits (S-layer) directly exposed to the extreme e nvironment. The elucidation of the crystal structure of this surface glycop rotein may provide important information on the survival strategies of thes e unusual micro-organisms. Before our investigations neither three-dimensio nal crystals have been obtained nor X-ray analyses were performed. Only ele ctron microscopic and computer image enhancement techniques have been appli ed to obtain structural information from crystalline two-dimensional S-laye r sheets. We describe here the successful crystallization of this surface g lycoprotein under microgravity conditions.