Identification and nucleotide sequence of a developmentally regulated gene encoding a eukaryotic histone H1-like protein from Chlamydia trachomatis.
A lambda gt11 recombinant library of Chlamydia trachomatis serovar L2 chromosomal DNA was screened with a 29-mer synthetic oligonucleotide specific to the N-terminal amino acids of a predominant 18-kDa chlamydial protein. One recombinant clone, designated lambda gt11/L2/RKA10, was selected on the basis of its strong hybridization signal. Restriction endonuclease analysis and complete nucleotide sequencing of the recombinant revealed a 2,633-bp insert containing one complete open reading frame (ORF2) and two partial ORFs (ORF1 and ORF3). The deduced amino acid sequence of ORF2 matched perfectly at its N-terminal end with the derived amino acid sequence. The 375-bp ORF is capable of encoding a protein comprising 125 amino acids with a molecular mass of 13,689. A sequence compatible with a Shine-Dalgarno ribosome-binding site was located 9 bp upstream from the initiation codon, while the sequence distal to ORF2 revealed a rho-independent terminator. The protein, designated CTH1, possesses an estimated pI of 10.71 due to its high lysine content. This highly basic protein contains no tryptophan or phenylalanine. A protein data base search identified significant homology between CTH1 and painted sea urchin histone H1. Northern (RNA) blot analysis of Chlamydia-infected host cells demonstrated transcripts at 12 h postinfection. The recombinant plasmid encoding ORF2 expressed a gene product of approximately 18 kDa, similar to the native chlamydial protein as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein appears to represent one of the few eukaryotic histonelike proteins described to date in prokaryotes.
Tao
S
S
Department of Pediatrics, University of Alberta, Edmonton, Canada.
Kaul
R
R
Wenman
W M
WM
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D002692:Chlamydia trachomatis / Q000235:genetics*; D005798:Genes, Bacterial; D006657:Histones / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012150:Polymorphism, Restriction Fragment Length; D012313:RNA / Q000032:analysis; D015183:Restriction Mapping; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D006657:Histones; D012313:RNA