title: The futalosine pathway played an important role in menaquinone biosynthesis during early prokaryote evolution.
abstract: Menaquinone (MK) is an important component of the electron-transfer system in prokaryotes. One of its precursors, 1,4-dihydroxy-2-naphthoate, can be synthesized from chorismate by the classical MK pathway. Interestingly, in some bacteria, chorismate can also be converted to 1,4-dihydroxy-6-naphthoate by four enzymes encoded by mqnABCD in an alternative futalosine pathway. In this study, six crucial enzymes belonging to these two independent nonhomologous pathways were identified in the predicted proteomes of prokaryotes representing a broad phylogenetic distribution. Although the classical MK pathway was found in 32.1% of the proteomes, more than twice the proportion containing the futalosine pathway, the latter was found in a broader taxonomic range of organisms (18 of 31 phyla). The prokaryotes equipped with the classical MK pathway were almost all aerobic or facultatively anaerobic, but those with the futalosine pathway were not only aerobic or facultatively anaerobic but also anaerobic. Phylogenies of enzymes of the classical MK pathway indicated that its genes in archaea were probably acquired by an ancient horizontal gene transfer from bacterial donors. Therefore, the organization of the futalosine pathway likely predated that of the classical MK pathway in the evolutionary history of prokaryotes.
authors.affiliation: Key Laboratory of Microbial Diversity in Southwest China, Ministry of Education and the Laboratory for Conservation and Utilization of Bio-Resources, Yunnan Institute of Microbiology, Yunnan University, Kunming, People's Republic of China.
authors.forename: Xiao-Yang
authors.initials: XY
authors.lastname: Zhi
authors.forename: Ji-Cheng
authors.initials: JC
authors.lastname: Yao
authors.forename: Shu-Kun
authors.initials: SK
authors.lastname: Tang
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Li
authors.forename: Wen-Jun
authors.initials: WJ
authors.lastname: Li
mesh_terms: D001105:Archaea / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D001419:Bacteria / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D020745:Genome, Archaeal; D016680:Genome, Bacterial; D009705:Nucleosides / Q000378:metabolism*; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D024482:Vitamin K 2 / Q000378:metabolism*
chemical_list: D009705:Nucleosides; D020543:Proteome; C122040:futalosine; D024482:Vitamin K 2
keywords: 1,4-dihydroxy-2-naphthoate; futalosine pathway; horizontal gene transfer; menaquinone; phylogeny