A tactile sensory system of Myxococcus xanthus involves an extracellular NAD(P)(+)-containing protein.
CsgA is a cell surface protein that plays an essential role in tactile responses during Myxococcus xanthus fruiting body formation by producing the morphogenic C-signal. The primary amino acid sequence of CsgA exhibits homology with members of the short-chain alcohol dehydrogenase (SCAD) family and several lines of evidence suggest that NAD(P)+ binding is essential for biological activity. First, the predicted CsgA secondary structure based on the 3 alpha/20 beta-hydroxysteroid dehydrogenase crystal structure suggests that the amino-terminal portion of the protein contains an NAD(P)+ binding pocket. Second, strains with csgA alleles encoding amino acid substitutions T6A and R10A in the NAD(P)+ binding pocket failed to develop. Third, exogenous MalE-CsgA rescues csgA development, whereas MalE-CsgA with the amino acid substitution CsgA T6A does not. Finally, csgA spore yield increased approximately 20% when containing 100 nM of MalE-CsgA was supplemented with 10 microM of NAD+ or NADP+. Conversely, 10 microM of NADH or NADPH delayed development for approximately 24 hr and depressed spore levels approximately 10%. Together, these results argue that NAD(P)+ binding is critical for C-signaling. S135 and K155 are conserved amino acids in the catalytic domain of SCAD members. Strains with csgA alleles encoding the amino acid substitutions S135T or K155R failed to develop. Furthermore, a MalE-CsgA protein containing CsgA S135T was not able to restore development to csgA cells. In conclusion, amino acids conserved in the coenzyme binding pocket and catalytic site are essential for C-signaling.
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics; D044943:Fatty Acid Desaturases; D058619:Maltose-Binding Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D016941:Myxococcus xanthus / Q000254:growth & development / Q000502:physiology*; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D014176:Protein Biosynthesis; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D013170:Spores; D014110:Touch; D014466:Ultraviolet Rays
D001426:Bacterial Proteins; D002352:Carrier Proteins; C063576:CsgA protein, Myxococcus xanthus; D058619:Maltose-Binding Proteins; D011993:Recombinant Fusion Proteins; D009249:NADP; D044943:Fatty Acid Desaturases