title: Function and evolution of two forms of SecDF homologs in Streptomyces coelicolor.
abstract: The general secretion (Sec) pathway plays a prominent role in bacterial protein export, and the accessory component SecDF has been shown to improve transportation efficiency. Inspection of Streptomyces coelicolor genome reveals the unexpected presence of two different forms of secDF homologous genes: one in fused form (secDF) and the other in separated form (secD and secF). However, the functional role of two SecDF homologs in S. coelicolor has not yet been determined. Transcriptional analysis of secDF homologs reveals that these genes are constitutively expressed. However, the transcript levels of secD and secF are much higher than that of secDF in S. coelicolor. Deletion of secDF or/and secD/secF in S. coelicolor did result in reduced secretion efficiency of Xylanase A and Amylase C, suggesting that they may have redundant functions for Sec-dependent translocation pathway. Moreover, our results also indicate that SecD/SecF plays a more prominent role than SecDF in protein translocation. Evolutionary analysis suggests that the fused and separated SecDF homologs in Streptomyces may have disparate evolutionary ancestries. SecD/SecF may be originated from vertical transmission of existing components from ancestor of Streptomyces species. However, SecDF may be derived from bacterial ancestors through horizontal gene transfer. Alternately, it is also plausible that SecDF may have arisen through additional gene duplication and fusion events. The acquisition of a second copy may confer a selective benefit to Streptomyces by enhancing protein transport capacity. Taken together, our results provide new insights into the potential biological function and evolutionary aspects of the prokaryotic SecDF complex.
authors.affiliation: Province Key Laboratory of Microbial Biochemistry and Metabolism Engineering, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Biology and South Texas Center for Emerging Infectious Diseases, University of Texas at San Antonio, San Antonio, Texas, United States of America; State Key Laboratory of Genetic Engineering and Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Department of Bioengineering, School of Food Sciences and Biotechnology, Zhejiang Gongshang University, Hangzhou, Zhejiang, China.
authors.forename: Yudong
authors.initials: Y
authors.lastname: Li
authors.affiliation: Province Key Laboratory of Microbial Biochemistry and Metabolism Engineering, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Sun
authors.affiliation: Province Key Laboratory of Microbial Biochemistry and Metabolism Engineering, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Province Key Laboratory of Microbial Biochemistry and Metabolism Engineering, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Longxian
authors.initials: L
authors.lastname: Lv
authors.affiliation: Department of Biology and South Texas Center for Emerging Infectious Diseases, University of Texas at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Genetic Engineering and Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China.
authors.forename: Libing
authors.initials: L
authors.lastname: Shen
authors.affiliation: Province Key Laboratory of Microbial Biochemistry and Metabolism Engineering, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Yong-Quan
authors.initials: YQ
authors.lastname: Li
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D005075:Biological Evolution; D016680:Genome, Bacterial / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D021381:Protein Transport / Q000235:genetics; D048372:Streptomyces coelicolor / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C075767:secD protein, Bacteria; C075768:secF protein, Bacteria