Teichuronic acid reducing terminal N-acetylglucosamine residue linked by phosphodiester to peptidoglycan of Micrococcus luteus

Abstract

Teichuronic acid-peptidoglycan complex isolated from Micrococcus luteus cells by lysozyme digestion in osmotically stabilized medium was treated with mild acid to cleave the linkage joining teichuronic acid to peptidoglycan. This labile linkage was shown to be the phosphodiester which joins N-acetylglucosamine, the residue located at the reducing end of the teichuronic acid, through its anomeric hydroxyl group to a 6-phosphomuramic acid, a residue of the glycan strand of peptidoglycan. 31P nuclear magnetic resonance spectroscopy of the lysozyme digest of cell walls demonstrated the presence of a phosphodiester which was converted to a phosphomonoester by the conditions which released teichuronic acid from cell walls. Reduction of acid-liberated reducing end groups by NaB3H4 followed by complete acid hydrolysis yielded [3H] glucosaminitol from the true reducing end residue of teichuronic acid and [3H]glucitol from the sites of fragmentation of teichuronic acid. The amount of N-acetylglucosamine detected was approximately stoichiometric with the amount of phosphate in the complex. Partial fragmentation of teichuronic acid provides an explanation of the previous erroneous identification of the reducing end residue.Micrococcus luteus cell walls consist of a peptidoglycan matrix to which teichuronic acid is covalently attached (2,8,12,13,29). Although the structure of the disaccharide repeat unit of teichuronic acid has been determined by chemical procedures (9) and confirmed by 13C nuclear magnetic resonance (NMR) spectroscopy (15), the precise nature of the linkage of teichuronic acid to peptidoglycan has remained in dispute. A small amount of phosphate is present in M. luteus cell walls (2), and much of it can be recovered from strong acid hydrolysates as muramic acid-6-phosphate (24). Glucosamine-6-phosphate has also been detected (18,27). A phosphodiester has been suggested as part of the covalent link between peptidoglycan and teichuronic acid in M. luteus (10,25,26) just as it serves to link teichoic acids and other cell wall polymers to peptidoglycan in other microorganisms (4,16,17,19,23).Nasir-ud-Din and Jeanloz (25) claimed that glucose is the reducing end residue of teichuronic acid which links to peptidoglycan through the phosphodiester. Later Nasirud-Din et al. (26) reported experimental results which purported to show that glucose is the reducing end residue of teichuronic acid. Evidence presented by Hase and Matsushima (10) indicated instead that the reducing end residue is N-acetylglucosamine. Our studies of in vitro teichuronic acid biosynthesis (14, 31) showed that biosynthesis depends on the initial step which incorporated N-acetylglucosamine-1-phosphate into a carrier lipid-activated intermediate. Furthermore, the N-acetylglucosamine residue remains in product teichuronic acid at the reducing end, suggesting that teichuronic acid in native cell walls has an N-acetylglucosamine residue at its potentially reducing terminal residue.We report here that the true reducing end residue of teichuronic ...

Proteins Encoded bySphingomonas elodeaATCC 31461rmlAandugpGGenes, Involved in Gellan Gum Biosynthesis, Exhibit both dTDP- and UDP-Glucose Pyrophosphorylase Activities

“…Interestingly, we found that the genetic organization of the overall region has no homologous regions in other prokaryotes, not even in N. aromaticivorans, which is phylogenetically close to S. elodea. Nevertheless, the four genes in the chromosomal region surrounding the ugpG gene were found in other organisms, organized in genetic clusters involved in the synthesis of capsular polysaccharides (9) or teichuronic acids (1,10,14) in gram-positive bacteria and lipopolysaccharides (2,28,33,37) in gram-negative bacteria. This observation raised the question of the putative involvement of this genomic region in the biosynthesis of a cell wall polysaccharide in S. elodea.…”

Genome Sequence of the Fleming Strain of Micrococcus luteus , a Simple Free-Living Actinobacterium

“…The polymer is attached to PG via the phosphate group of a reducing terminal trisaccharide consisting of two ManNAcU residues and an N-acetylglucosamine (GlcNAc) phosphate residue (33). The TUA operon of B. subtilis provides few useful search queries, and the genes concerned with TUA biosynthesis in most other organisms have not been well characterized.…”

Polymer length of teichuronic acid released from cell walls of Micrococcus luteus

“…Undoubtedly, native teichuronic acid has a range of polymer chain lengths, but some of the polydispersity observed is the consequence of fragmentation which occurs concomitantly with release of teichuronic acid from the cell wall. All conditions tested for cleavage of the phosphodiester (i.e., the bond by which the teichuronic acid is attached to peptidoglycan [7]) also show evidence of some simultaneous teichuronic acid fragmentation. Such fragmentation in mild acid is expected to involve cleavage of a-D-glucosidic bonds preferentially to N-acetyl-P-D-mannosaminiduronic acid bonds because of the preferential resistance of the glycosides of uronic acids (1,2,16).…”