Crystal structure of the transcription factor sc-mtTFB offers insights into mitochondrial transcription.
Although it is commonly accepted that binding of mitochondrial transcription factor sc-mtTFB to the mitochondrial RNA polymerase is required for specific transcription initiation in Saccharomyces cerevisiae, its precise role has remained undefined. In the present work, the crystal structure of sc-mtTFB has been determined to 2.6 A resolution. The protein consists of two domains, an N-terminal alpha/beta-domain and a smaller domain made up of four alpha-helices. Contrary to previous predictions, sc-mtTFB does not resemble Escherichia coli sigma-factors but rather is structurally homologous to rRNA methyltransferase ErmC'. This suggests that sc-mtTFB functions as an RNA-binding protein, an observation standing in contradiction to the existing model, which proposed a direct interaction of sc-mtTFB with the mitochondrial DNA promoter. Based on the structure, we propose that the promoter specificity region is located on the mitochondrial RNA polymerase and that binding of sc-mtTFB indirectly mediates interaction of the core enzyme with the promoter site.
Schubot
F D
FD
Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA.
Chen
C J
CJ
Rose
J P
JP
Dailey
T A
TA
Dailey
H A
HA
Wang
B C
BC
D000595:Amino Acid Sequence; D001665:Binding Sites; D003460:Crystallization; D018360:Crystallography, X-Ray; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor / Q000737:chemistry; D014157:Transcription Factors / Q000737:chemistry*; D014158:Transcription, Genetic
C071720:MTF1 protein, S cerevisiae; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases