title: Structure of the essential diversity-generating retroelement protein bAvd and its functionally important interaction with reverse transcriptase.
abstract: Diversity-generating retroelements (DGRs) are the only known source of massive protein sequence variation in prokaryotes. These elements transfer coding information from a template region (TR) through an RNA intermediate to a protein-encoding variable region. This retrohoming process is accompanied by unique adenine-specific mutagenesis and, in the prototypical BPP-1 DGR, requires a reverse transcriptase (bRT) and an accessory variability determinant (bAvd) protein. To understand the role of bAvd, we determined its 2.69 Å resolution structure, which revealed a highly positively charged pentameric barrel. In accordance with its charge, bAvd bound both DNA and RNA, albeit without a discernable sequence preference. We found that the coding sequence of bAvd functioned as part of TR but identified means to mutate bAvd without affecting TR. This mutational analysis revealed a strict correspondence between retrohoming and interaction of bAvd with bRT, suggesting that the bRT-bAvd complex is important for DGR retrohoming.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Maher
authors.initials: M
authors.lastname: Alayyoubi
authors.forename: Huatao
authors.initials: H
authors.lastname: Guo
authors.forename: Sanghamitra
authors.initials: S
authors.lastname: Dey
authors.forename: Talin
authors.initials: T
authors.lastname: Golnazarian
authors.forename: Garrett A
authors.initials: GA
authors.lastname: Brooks
authors.forename: Andrew
authors.initials: A
authors.lastname: Rong
authors.forename: Jeffery F
authors.initials: JF
authors.lastname: Miller
authors.forename: Partho
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D019943:Amino Acid Substitution; D001435:Bacteriophages / Q000201:enzymology*; D001884:Bordetella / Q000821:virology*; D018360:Crystallography, X-Ray; D004277:DNA, Single-Stranded / Q000737:chemistry; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D012313:RNA / Q000737:chemistry; D012194:RNA-Directed DNA Polymerase / Q000737:chemistry*; D018626:Retroelements; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D004277:DNA, Single-Stranded; D018626:Retroelements; D014764:Viral Proteins; D012313:RNA; D012194:RNA-Directed DNA Polymerase