The Rickettsia type IV secretion system: unrealized complexity mired by gene family expansion.
Many prokaryotes utilize type IV secretion systems (T4SSs) to translocate substrates (e.g. nucleoprotein, DNA, protein) across the cell envelope, and/or to elaborate surface structures (i.e. pili or adhesins). Among eight distinct T4SS classes, P-T4SSs are typified by the Agrobacterium tumefaciens vir T4SS, which is comprised of 12 scaffold components (VirB1-VirB11, VirD4). While most P-T4SSs include all 12 Vir proteins, some differ from the vir archetype by either containing additional scaffold components not analogous to Vir proteins or lacking one or more of the Vir proteins. In a special case, the Rickettsiales vir homolog (rvh) P-T4SS comprises unprecedented gene family expansion. rvh contains three families of gene duplications (rvhB9, rvhB8, rvhB4): RvhB9,8,4-I are conserved relative to equivalents in other P-T4SSs, while RvhB9,8,4-II have evolved atypical features that deviate substantially from other homologs. Furthermore, rvh contains five VirB6-like genes (rvhB6a-e), which are tandemly arrayed and contain large N- and C-terminal extensions. Our work herein focuses on the complexity underpinned by rvh gene family expansion. Furthermore, we describe an RvhB10 insertion, which occurs in a region that forms the T4SS pore. The significance of these curious properties to rvh structure and function is evaluated, shedding light on a highly complex T4SS.
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA JGillespie@som.umaryland.edu.
Joseph J
JJ
Gillespie
Seattle Structural Genomics Center for Infectious Disease, 307 Westlake Ave North, Seattle, WA 98109, USA Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, WA 98109, USA.
Isabelle Q H
IQ
Phan
Department of Biology, West Virginia University, Life Sciences Building, PO Box 6057, Morgantown, WV 26506-6201, USA.
Timothy P
TP
Driscoll
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA.
Mark L
ML
Guillotte
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA.
Stephanie S
SS
Lehman
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA.
Kristen E
KE
Rennoll-Bankert
Seattle Structural Genomics Center for Infectious Disease, 307 Westlake Ave North, Seattle, WA 98109, USA Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, WA 98109, USA.
Sandhya
S
Subramanian
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA.
Magda
M
Beier-Sexton
Seattle Structural Genomics Center for Infectious Disease, 307 Westlake Ave North, Seattle, WA 98109, USA Center for Infectious Disease Research (formerly Seattle Biomedical Research Institute), Seattle, WA 98109, USA.
Peter J
PJ
Myler
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA.
M Sayeedur
MS
Rahman
Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W. Baltimore St., HSF I Suite 380, Baltimore, MD 21201, USA.
Abdu F
AF
Azad
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020440:Gene Duplication; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D005798:Genes, Bacterial; D008958:Models, Molecular; D005810:Multigene Family; D016254:Mutagenesis, Insertional; D056510:Position-Specific Scoring Matrices; D011485:Protein Binding; D011487:Protein Conformation; D000072417:Protein Domains; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D021381:Protein Transport; D012281:Rickettsia / Q000502:physiology*; D012282:Rickettsia Infections / Q000382:microbiology; D000069319:Type IV Secretion Systems
D001426:Bacterial Proteins; D000069319:Type IV Secretion Systems
Rickettsia; Rickettsiales vir homolog; gene duplication; obligate intracellular bacteria; pathogenesis; type IV secretion system