Complete glycan structure of the S-layer glycoprotein of aneurinibacillus thermoaerophilus GS4-97

Abstract

Isolate GS4-97 was purified from an extraction juice sample of an Austrian beet sugar factory and affiliated to the newly described species Aneurinibacillus thermoaerophilus. It is closely related to the type strain of this species, A. thermoaerophilus L420-91(T), and possesses a square surface layer (S-layer) array composed of identical glycoprotein monomers as its outermost cell envelope component. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified S-layer showed an apparent molecular mass of ~ 109,000. After thorough proteolytic degradation of this material by pronase E and purification of the reaction mixture by gel permeation, chromato-focusing, and reversed-phase chromatography, a homogeneous glycopeptide fraction was obtained which was subjected to one- and two-dimensional nuclear magnetic resonance spectroscopy. The combined chemical and spectroscopic evidence, together with N-terminal sequencing, suggest the following structure of the O-glycosidically linked S-layer glycan chain of the glycopeptide: This is the first description of a β-D-GalNAc-Thr linkage in glycoproteins.