title: Role of the D-alanyl carrier protein in the biosynthesis of D-alanyl-lipoteichoic acid.
abstract: D-Alanyl-lipoteichoic acid (D-alanyl-LTA) is a widespread macroamphiphile which plays a vital role in the growth and development of gram-positive organisms. The biosynthesis of this polymer requires the enzymic activation of D-alanine for its transfer to the membrane-associated LTA (mLTA). A small, heat-stable, and acidic protein that is required for this transfer was purified to greater than 98% homogeneity from Lactobacillus casei ATCC 7469. This protein, previously named the D-alanine-membrane acceptor ligase (V. M. Reusch, Jr., and F. C. Neuhaus, J. Biol. Chem. 246:6136-6143, 1971), functions as the D-alanyl carrier protein (Dcp). The amino acid composition, beta-alanine content, and N-terminal sequence of this protein are similar to those of the acyl carrier proteins (ACPs) of fatty acid biosynthesis. The isolation of Dcp and its derivative, D-alanyl approximately Dcp, has allowed the characterization of two novel reactions in the pathway for D-alanyl-mLTA biosynthesis: (i) the ligation of Dcp with D-alanine and (ii) the transfer of D-alanine from D-alanyl approximately Dcp to a membrane acceptor. It has not been established whether the membrane acceptor is mLTA or another intermediate in the pathway for D-alanyl-mLTA biosynthesis. Since the D-alanine-activating enzyme (EC 6.1.1.13) catalyzes the ligation reaction, this enzyme functions as the D-alanine-Dcp ligase (Dcl). Dcl also ligated the ACPs from Escherichia coli, Vibrio harveyi, and Saccharopolyspora erythraea with D-alanine. In contrast to the relaxed specificity of Dcl in the ligation reaction, the transfer of D-alanine to the membrane acceptor was highly specific for Dcp and did not occur with other ACPs. This transfer was observed by using only D-[14C]alanyl approximately Dcp and purified L. casei membranes. Thus, D-alanyl approximately Dcp is an essential intermediate in the transfer of D-alanine from Dcl to the membrane acceptor. The formation of D-alanine esters of mLTA provides a mechanism for modulating the net anionic charge in the cell wall.
authors.affiliation: Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, Illinois 60208.
authors.forename: M P
authors.initials: MP
authors.lastname: Heaton
authors.forename: F C
authors.initials: FC
authors.lastname: Neuhaus
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007780:Lacticaseibacillus casei / Q000378:metabolism*; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D011994:Recombinant Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013682:Teichoic Acids / Q000096:biosynthesis*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C085651:D-alanyl carrier protein, bacteria; D011994:Recombinant Proteins; D013682:Teichoic Acids; C026244:alanyl-lipoteichoic acid