The Cell Wall Polymer of the Extremely Halophilic Archaeon Natronococcus occultus

Open Access
Publisher Website
Google Scholar
Abstract
The cell wall polymer of Natronococcus occultus (DSM 3396) consists of L‐glutamate, N ‐acetyl‐d‐glucosamine, N ‐acetyl‐d‐galactosamine, d‐galacturonic acid, d‐glucuronic acid and d‐glucose in a molar ratio of 5:7:1:8:0.5:0.3. Partial acid hydrolysis of the cell wall polymer produced soluble fragments that could be separated by HPLC. A γ‐glutamyl dipeptide was isolated. In the intact cell wall polymer, the glutamate residues form a poly‐(γ‐glutamine) chain with a length of about 60 monomers, which corresponds to a relative molecular mass of approximately 7700 Da. Two other soluble dimeric fragments, composed of glutamate and either glucosamine or galactosamine in a molar ratio of 1:1, were purified from the hydrolysate, suggesting the presence of two different oligosaccharides linked to the poly‐(γ‐glutamine) chain of the intact polymer. The analysis of additional fragments, which were composed of an amino sugar and galacturonic acid or glucose indicated that one oligosaccharide consisted of a glucosamine pentamer in an α‐1,3 linkage at the reducing end and an oligomer with at least five β‐1,4‐linked galacturonic acid residues at the non‐reducing end. The second oligosaccharide was comprised of a galactosamine dimer in a β‐1,3 linkage at the reducing end and a maltose unit at the non‐reducing end. Both oligosaccharides were linked to the α‐amide group of the glutamine residues of the poly‐(γ‐glutamine) chain. The whole cell wall polymer, which represents a novel type of natural glycoconjugate, has a relative molecular mass of 54kDa.

This publication has 19 references indexed in Scilit: