title: Characterization of genetic determinants for R body synthesis and assembly in Caedibacter taeniospiralis 47 and 116.
abstract: Caedibacter taeniospiralis, an obligate bacterial endosymbiont of Paramecium tetraurelia, confers a killing trait upon its host paramecium. Type 51 R bodies (refractile inclusion bodies) are synthesized by these endosymbionts and are required for expression of the killing trait. The nucleotide sequence of the genetic determinants for type 51 R body synthesis and assembly was determined for C. taeniospiralis 47 and 116. Three independently transcribed genes (rebA, rebB, and rebC) were characterized. To date these are the only genes from C. taeniospiralis to be sequenced and characterized. DNA regulatory regions are recognized by Escherichia coli, and codon usage appears similar to that in E. coli. A fourth open reading frame with appropriate regulatory sequences was found within the reb locus, but no evidence was obtained to suggest that this putative gene is expressed in E. coli. The R body-encoding sequences from both strains are identical. Two-dimensional gel electrophoresis of deletion derivatives shows that two polymerization events are involved in R body assembly. One polymerization event requires only RebB and RebC; the other requires all three proteins. Expression of RebC is necessary for the posttranslational modification of RebA and RebB into species with three and two different molecular weights, respectively. In the presence of RebC, each species of RebB with a different molecular weight has six different isoelectric points.
authors.affiliation: Department of Microbiology, School of Medicine, University of South Dakota, Vermillion 57069.
authors.forename: D P
authors.initials: DP
authors.lastname: Heruth
authors.forename: F R
authors.initials: FR
authors.lastname: Pond
authors.forename: J A
authors.initials: JA
authors.lastname: Dilts
authors.forename: R L
authors.initials: RL
authors.lastname: Quackenbush
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000235:genetics*; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial / Q000235:genetics*; D005815:Genetic Code; D002479:Inclusion Bodies / Q000502:physiology*; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016805:Paramecium tetraurelia / Q000382:microbiology; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D017385:Sequence Homology; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; C087726:RebA protein, Caedibacter taeniospiralis; C087727:RebB protein, Caedibacter taeniospiralis; C087729:RebC protein, Caedibacter taeniospiralis; D011994:Recombinant Proteins