{"title":"Processing of tRNA in prokaryotes and eukaryotes.","authors":"M P Deutscher","doi":"10.3109/10409238409110269","DOIUrl":"https://doi.org/10.3109/10409238409110269","url":null,"abstract":"<p><p>Considerable progress has been made in defining the steps in the conversion of a tRNA precursor to a mature tRNA. These steps, which differ in different systems, include removal of precursor-specific residues from the 5' and 3' termini of the initial transcript, addition of the 3'-C-C-A terminus, splicing of intervening sequences, and modification of nucleotide residues. Despite these advances in defining the \"pathways\" of tRNA processing, relatively little is known about most of the enzymes actually involved in these processing steps. In this article I describe the sequence of reactions needed to convert the initial tRNA transcript to a functional, mature tRNA, and discuss the specificity and properties of enzymes known to be involved in this process. In addition, I speculate on the expected specificities of other enzymes involved in tRNA processing which have not yet been identified, and on the structural organization of the processing machinery.</p>","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"17 1","pages":"45-71"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238409110269","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17161314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The synthesis and biology of fluorinated prostacyclins.","authors":"W. E. Barnette","doi":"10.3109/10409238409102802","DOIUrl":"https://doi.org/10.3109/10409238409102802","url":null,"abstract":"Fluorination has been used extensively in the steroid field to alter and/or enhance activity and to increase chemical or biological stability taking advantage of the similarity in size between hydrogen and fluorine and its strong electronegativity. Thus, it is not surprising to find that the same principle has been applied to prostaglandins, more specifically prostacyclin. The specific activity and high instability of Prostacyclin make it an ideal candidate for similar fluorination techniques. The design and preparation of fluorinated analogs with the aim of improving the chemical and metabolic stability of this important molecule will be discussed.","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"94 1","pages":"201-35"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238409102802","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69419416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Structural and functional aspects of domain motions in proteins.","authors":"W S Bennett, R Huber","doi":"10.3109/10409238409117796","DOIUrl":"https://doi.org/10.3109/10409238409117796","url":null,"abstract":"<p><p>Three distinct categories of large-scale flexibility in proteins have been documented by single-crystal X-ray diffraction studies: the relatively free movement of essentially rigid globular domains that are connected by a flexible segment of polypeptide, the reorientation of essentially rigid domains among a few distinct conformations, and the concerted transition of a contiguous region of the surface of a protein from a disordered state to an ordered state. In a number of examples, well-defined functions can be assigned to these large-scale structural changes. The occurrence of such motions in proteins of known structure is reviewed, and the best-studied examples are discussed in detail to allow a critical evaluation of the methods used to identify and study these motions.</p>","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"15 4","pages":"291-384"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238409117796","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17385839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The proton inventory technique.","authors":"K S Venkatasubban, R L Schowen","doi":"10.3109/10409238409110268","DOIUrl":"https://doi.org/10.3109/10409238409110268","url":null,"abstract":"<p><p>The proton inventory technique uses the dependence of enzymic reaction rate on the atom fraction of deuterium present in mixtures of protium oxide and deuterium oxide to deduce for simple cases the number of exchangeable hydrogenic sites that produce isotope effects, and the magnitude of the isotope effect generated at each site. For more complex cases, other information, such as the participation of more than a single step in limiting the rate, may be obtained. The background of the method, the conduct of the experiments and the interpretation of the results are briefly reviewed. The method is then illustrated in its application to various enzyme systems by a series of case histories.</p>","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"17 1","pages":"1-44"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238409110268","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17161313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Sucrase-isomaltase: a stalked intrinsic protein of the brush border membrane.","authors":"H Hauser, G Semenza","doi":"10.3109/10409238309102798","DOIUrl":"https://doi.org/10.3109/10409238309102798","url":null,"abstract":"<p><p>The isolation and purification of sucrase-isomaltase from brush border membrane is described and the physicochemical properties of the pure enzyme are discussed. Our present understanding of the mode of association of the intrinsic membrane protein sucrase-isomaltase with the brush border membrane will be the central point of this contribution. The assembly of sucrase-isomaltase into phospholipid bilayers has been reported to result in a model membrane system which resembles the \"native\" brush border membrane as regards the mode of lipid-protein interaction. The physicochemical properties of this reconstituted model membrane will be compared to the in vivo situation as represented by brush border membrane vesicles routinely isolated from small intestinal brush borders. The biosynthetic mechanism will be discussed.</p>","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"14 4","pages":"319-45"},"PeriodicalIF":0.0,"publicationDate":"1983-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238309102798","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17418597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Conformation and activity of beta-lactam antibiotics.","authors":"V S Rao, T K Vasudevan","doi":"10.3109/10409238309102793","DOIUrl":"https://doi.org/10.3109/10409238309102793","url":null,"abstract":"","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"14 3","pages":"173-206"},"PeriodicalIF":0.0,"publicationDate":"1983-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238309102793","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17414231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Transcription of mitochondrial DNA.","authors":"H F Tabak, L A Grivell, P Borst","doi":"10.3109/10409238309102797","DOIUrl":"https://doi.org/10.3109/10409238309102797","url":null,"abstract":"<p><p>While mitochondrial DNA (mtDNA) is the simplest DNA in nature, coding for rRNAs and tRNAs, results of DNA sequence, and transcript analysis have demonstrated that both the synthesis and processing of mitochondrial RNAs involve remarkably intricate events. At one extreme, genes in animal mtDNAs are tightly packed, both DNA strands are completely transcribed (symmetric transcription), and the appearance of specific mRNAs is entirely dependent on processing at sites signalled by the sequences of the tRNAs, which abut virtually every gene. At the other extreme, gene organization in yeast (Saccharomyces) is anything but compact, with long stretches of AT-rich DNA interspaced between coding sequences and no obvious logic to the order of genes. Transcription is asymmetric and several RNAs are initiated de novo. Nevertheless, extensive RNA processing occurs due largely to the presence of split genes. RNA splicing is complex, is controlled by both mitochondrial and nuclear genes, and in some cases is accompanied by the formation of RNAs that behave as covalently closed circles. The present article reviews current knowledge of mitochondrial transcription and RNA processing in relation to possible mechanisms for the regulation of mitochondrial gene expression.</p>","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"14 4","pages":"297-317"},"PeriodicalIF":0.0,"publicationDate":"1983-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238309102797","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17261062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"DNA topoisomerases--enzymes that catalyse the breaking and rejoining of DNA.","authors":"L F Liu","doi":"10.3109/10409238309102799","DOIUrl":"https://doi.org/10.3109/10409238309102799","url":null,"abstract":"","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"15 1","pages":"1-24"},"PeriodicalIF":0.0,"publicationDate":"1983-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238309102799","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17380357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Chloramphenicol acetyltransferase: enzymology and molecular biology.","authors":"W V Shaw","doi":"10.3109/10409238309102789","DOIUrl":"https://doi.org/10.3109/10409238309102789","url":null,"abstract":"<p><p>Naturally occurring chloramphenicol resistance in bacteria is normally due to the presence of the antibiotic inactivating enzyme chloramphenicol acetyltransferase (CAT) which catalyzes the acetyl-S-CoA-dependent acetylation of chloramphenicol at the 3-hydroxyl group. The product 3-acetoxy chloramphenicol does not bind to bacterial ribosomes and is not an inhibitor of peptidyltransferase. The synthesis of CAT is constitutive in E. coli and other Gram-negative bacteria which harbor plasmids bearing the structural gene for the enzyme, whereas Gram-positive bacteria such as staphylococci and streptococci synthesize CAT only in the presence of chloramphenicol and related compounds, especially those with the same stereochemistry of the parent compound and which lack antibiotic activity and a site of acetylation (3-deoxychloramphenicol). Studies of the primary structures of CAT variants suggest a marked degree of heterogeneity but conservation of amino acid sequence at and near the putative active site. All CAT variants are tetramers composed in each case of identical polypeptide subunits consisting of approximately 220 amino acids. The catalytic mechanism does not appear to involve an acyl-enzyme intermediate although one or more cysteine residues are protected from thiol reeagents by substrates. A highly reactive histidine residue has been implicated in the catalytic mechanism.</p>","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"14 1","pages":"1-46"},"PeriodicalIF":0.0,"publicationDate":"1983-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238309102789","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17401511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Sterol structure and membrane function.","authors":"K E Bloch","doi":"10.3109/10409238309102790","DOIUrl":"https://doi.org/10.3109/10409238309102790","url":null,"abstract":"","PeriodicalId":75744,"journal":{"name":"CRC critical reviews in biochemistry","volume":"14 1","pages":"47-92"},"PeriodicalIF":0.0,"publicationDate":"1983-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/10409238309102790","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"17401512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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