Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The poliovirus-encoded, membrane associated polypeptide 2C is required for viral replication. We have previously established that, while the 2C protein lacks a defined membrane binding domain, the N-terminal region containing a putative amphipathic helix plays an important role in membrane binding both in vivo and in vitro. In order to determine whether the N-terminal region is sufficient for membrane binding, we have made fusion constructs between this region of 2C (amino acids 1-72 and 1-88) and a soluble protein, chloramphenicol acetyltransferase (CAT). The ability of CAT and the fusion polypeptides to bind to membranes was examined by in vitro translation in the presence of microsomal membrane. While CAT was found in the soluble fraction, both 2C/CAT fusion constructs (1-72/CAT and 1-88/CAT) were membrane associated, suggesting that the N-terminal region of 2C was sufficient to impart membrane binding. To confirm these results in vivo, CAT, 1-72/CAT, and 1-88/CAT were expressed in HeLa cells and their localization was examined using indirect immunofluorescence. Results presented here demonstrate that, while CAT is expressed throughout the cell, 1-72/CAT and 1-88/CAT constructs are capable of localizing to the endoplasmic reticulum (ER) area in transfected cells in the absence of other poliovirus proteins. These results suggest that the first 72 amino acids of 2C contain a membrane binding domain that is capable of targeting soluble proteins to the ER region of the cell.
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PMID:Amino-terminal region of poliovirus 2C protein is sufficient for membrane binding. 969 29

Previously, we demonstrated that explanted bovine retinal pigment epithelium (RPE) cells lose RPE65 protein, a major microsomal protein specific to RPE, while the RPE65 mRNA remains, suggesting posttranscriptional regulation of RPE65 expression in vitro. Accordingly, we analyze here the effect of the 5'- and 3'-untranslated regions (UTRs) of RPE65 mRNA on translational efficiency using in vitro translation systems. We compared the levels of translation products and mRNA stability among RPE65 transcripts containing deletions of the 5'- and 3'-UTRs. First, the 5'-UTR does not affect translational efficiency. However, the 3'-UTR does influence translation efficiency. A putative translation inhibitory element (TIE) is contained within the 170-nucleotide (nt) sequence downstream of the stop codon. There is also a weak destabilizing effect that is associated with the region 3' to the putative TIE. But the effect of this is much less than that of the TIE. This TIE, however, does not inhibit translation of the heterologous chloramphenicol acetyltransferase gene, suggesting that a specific interaction with the upstream RPE65 coding sequence, or its product, may be required. Thus, the posttranscriptional regulation of RPE65 mRNA expression observed in cultured RPE may be via a mechanism of translational inhibition.
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PMID:Role of the 3'-untranslated region of RPE65 mRNA in the translational regulation of the RPE65 gene: identification of a specific translation inhibitory element. 972 Nov 81

Mitochondrial carnitine palmitoyltransferase I (CPT I) and microsomal carnitine acyltransferase I (CAT I) regulate the entry of fatty acyl moieties into their respective organelles. Thus, CPT I and CAT I occupy prominent positions in the pathways responsible for energy generation in mitochondria and the assembly of VLDL in the endoplasmic reticulum, respectively. Previous attempts to determine the intrinsic kinetic properties of CPT I and CAT I have been hampered by the occurrence of sigmoidal velocity curves. This was overcome, in this study, by the inclusion of recombinant acyl-CoA binding protein in the assay medium. For the first time, we have determined the concentrations of total functional enzyme (E(t)) by specific radiolabeling of the active site, the dissociation constants (K(d)) and the turnover numbers of CPT I and CAT I toward the CoA esters of oleic acid (C18:1) and docosahexaenoic acid (C22:6). The data show that carnitine inhibits CAT I at physiological concentrations which are not inhibitory to CPT I. Thus, carnitine concentration is likely to be a significant factor in determining the partitioning of acyl-CoAs between mitochondria and microsomes, a role which has not been previously recognized. Moreover, the finding that CAT I elicits a lower turnover toward the CoA ester of C22:6 (25 s(-)(1)) than toward that of C18:1 (111 s(-)(1)), while having similar K(d) values, suggests the use of this polyunsaturated fatty acid to inhibit VLDL biosynthesis.
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PMID:Evaluation of the affinity and turnover number of both hepatic mitochondrial and microsomal carnitine acyltransferases: relevance to intracellular partitioning of acyl-CoAs. 1062 48


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