RESUMO
Translation, that is biosynthesis of polypeptides in accordance with information encoded in the genome, is one of the most important processes in the living cell, and it has been in the spotlight of international research for many years. The mechanisms of protein biosynthesis in bacteria and in the eukaryotic cytoplasm are now understood in great detail. However, significantly less is known about translation in eukaryotic mitochondria, which is characterized by a number of unusual features. In this review, we summarize current knowledge about mitochondrial translation in different organisms while paying special attention to the aspects of this process that differ from cytoplasmic protein biosynthesis.
Assuntos
Mitocôndrias/metabolismo , Proteínas Mitocondriais/biossíntese , Animais , Humanos , Mitocôndrias/genética , Proteínas Mitocondriais/genética , Elongação Traducional da Cadeia Peptídica , Iniciação Traducional da Cadeia Peptídica , Terminação Traducional da Cadeia Peptídica , RNA/biossínteseRESUMO
Multisubunit RNA polymerase transcribes DNA in all living organisms. RNA polymerase is also known to synthesize DNA replication primers in some replication systems, a function that is commonly performed by primases. There are two unrelated types of primases, the bacterial and eukaryal-archaeal types; RNA polymerase has no evolutionary relationship to either type. Here we discuss the mechanism of primer synthesis by RNA polymerase and compare it to mechanisms used by primases of both types as well as to the mechanisms used by RNA polymerase during transcription.
Assuntos
DNA Primase/metabolismo , RNA Polimerases Dirigidas por DNA/metabolismo , Animais , DNA/metabolismo , Primers do DNA/biossíntese , HumanosRESUMO
Mycobacterium tuberculosis RNA polymerase is 1,000-fold more sensitive to rifampin than Escherichia coli RNA polymerase. Chimeric E. coli RNA polymerase in which the beta-subunit segment encompassing rifampin regions I and II (amino acids [aa] 463 through 590) was replaced with the corresponding region from M. tuberculosis (aa 382 through 509) did not show an increased sensitivity to the antibiotic. Thus, the difference in amino acid sequence between the rifampin regions I and II of the two species does not account for the difference in rifampin sensitivity of the two polymerases.
