title: Evidence that a chaperone-usher-like pathway of Myxococcus xanthus functions in spore coat formation.
abstract: Many bacteria use the chaperone-usher (CU) secretion pathway to assemble on their surfaces typical or atypical fimbrial organelles. Four consecutive genes of Myxococcus xanthus DK1622, MXAN3885-3882, were predicted to constitute an operon encoding a CU-like system involved in the assembly of the spore coat; however, experimental evidence supporting this hypothesis was lacking. In this study, co-transcription of MXAN3885-3883 was verified, and we found that this operon was expressed 12-15 h after initiation of M. xanthus development under conditions of stringent starvation. The MXAN3885 protein, which is highly homologous to, but expressed earlier than, the spore coat protein U of another M. xanthus strain, DZF1, was present mainly on the outer surface of myxospores. Inactivation of MXAN3883, encoding a putative outer membrane usher, inhibited assembly of MXAN3885 protein on spore surfaces and caused certain morphological alterations in the spore coat. Hence, the CU-like pathway in M. xanthus indeed functions in spore coat biogenesis. Based on chaperone amino acid sequence comparisons, our analysis suggests that the structural basis of the M. xanthus CU-like pathway for spore coat assembly may be different from that of most surface structures assembled by classical CU systems.
authors: Department of Biochemistry, School of Medicine, Southeast University, Nanjing, Jiangsu 210009, PR China.|Key laboratory of Ministry of Education for Developmental Genes and Human Diseases, Southeast University, Nanjing, Jiangsu 210009, PR China.
authors: Xiaoyan
authors: X
authors: Leng
authors: Department of Biochemistry, School of Medicine, Southeast University, Nanjing, Jiangsu 210009, PR China.|Key laboratory of Ministry of Education for Developmental Genes and Human Diseases, Southeast University, Nanjing, Jiangsu 210009, PR China.
authors: Wei
authors: W
authors: Zhu
authors: Department of Biochemistry, School of Medicine, Southeast University, Nanjing, Jiangsu 210009, PR China.|Key laboratory of Ministry of Education for Developmental Genes and Human Diseases, Southeast University, Nanjing, Jiangsu 210009, PR China.
authors: Jing
authors: J
authors: Jin
authors: Department of Biochemistry, School of Medicine, Southeast University, Nanjing, Jiangsu 210009, PR China.|Key laboratory of Ministry of Education for Developmental Genes and Human Diseases, Southeast University, Nanjing, Jiangsu 210009, PR China.
authors: Xiaohua
authors: X
authors: Mao
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D015151:Immunoblotting; D008854:Microscopy, Electron; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D016941:Myxococcus xanthus / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009876:Operon; D016133:Polymerase Chain Reaction; D016415:Sequence Alignment; D013171:Spores, Bacterial / Q000254:growth & development* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones; C046032:Myxococcus spore coat proteins; C069254:protein U, Myxococcus