Polymerization of mycobacterial arabinogalactan and ligation to peptidoglycan.
The cell wall of Mycobacterium spp. consists predominately of arabinogalactan chains linked at the reducing ends to peptidoglycan via a P-GlcNAc-(alpha1-3)-Rha linkage unit (LU) and esterified to a variety of mycolic acids at the nonreducing ends. Several aspects of the biosynthesis of this complex have been defined, including the initial formation of the LU on a polyprenyl phosphate (Pol-P) molecule followed by the sequential addition of galactofuranosyl (Galf) units to generate Pol-P-P-LU-(Galf)1,2,3, etc. and Pol-P-P-LU-galactan, catalyzed by a bifunctional galactosyltransferase (Rv3808c) capable of adding alternating 5- and 6-linked Galf units. By applying cell-free extracts of Mycobacterium smegmatis, containing cell wall and membrane fragments, and differential labeling with UDP-[14C]Galp and recombinant UDP-Galp mutase as the source of [14C]Galf for galactan biosynthesis and 5-P-[14C]ribosyl-P-P as a donor of [14C]Araf for arabinan synthesis, we now demonstrate sequential synthesis of the simpler Pol-P-P-LU-(Galf)n glycolipid intermediates followed by the Pol-P-P-LU-arabinogalactan and, finally, ligation of the P-LU-arabinogalactan to peptidoglycan. This first time demonstration of in vitro ligation of newly synthesized P-LU-arabinogalactan to newly synthesized peptidoglycan is a necessary forerunner to defining the genetics and enzymology of cell wall polymer-peptidoglycan ligation in Mycobacterium spp. and examining this step as a target for new antibacterial drugs.
Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, Colorado 80523-1682, USA.
Tetsuya
T
Yagi
Sebabrata
S
Mahapatra
Katarina
K
Mikusova
Dean C
DC
Crick
Patrick J
PJ
Brennan
D001665:Binding Sites; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D005685:Galactans / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D009161:Mycobacterium / Q000737:chemistry / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry; D012995:Solubility
D005685:Galactans; D010457:Peptidoglycan; D011108:Polymers; C005653:arabinogalactan