Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The carbamoylphosphate synthetase-aspartate transcarbamylase-dihydroorotase (CAD) gene encodes a tri-functional protein catalyzing the first three steps in de novo pyrimidine biosynthesis. Studies correlating CAD gene expression with cellular proliferation indicate the importance of understanding the regulation of the CAD gene. As a first step, the structure of the promoter region of the Syrian hamster CAD gene has been determined. Sequence analysis of 1671 base pairs of DNA revealed that the CAD promoter region is very GC rich. Primer extension analysis indicated that the transcription initiation site of the CAD gene is downstream from two GC boxes (consensus binding sites for the transcription factor Sp1). There is no TATA box appropriately spaced upstream from the transcription initiation site. Using RNase protection mapping, S1 nuclease analysis, and comparison to consensus splice donor/acceptor sites, the 5' end of the CAD gene has been determined to consist of a 241-base pair first exon, a 187-base pair first intron, a 140-base pair second exon, and a second intron that extends at least three kilobase pairs. Using conditions optimized for this GC-rich promoter, accurate transcription can be achieved in vitro. Analysis of CAD promoter deletions indicated that sequences extending only 114 base pairs upstream and 225 base pairs downstream from the transcription initiation site are sufficient for accurate and efficient transcription in vitro. DNase I footprinting reactions using this promoter fragment have identified three regions that bind proteins in a HeLa nuclear extract.
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PMID:Characterization of the 5' end of the growth-regulated Syrian hamster CAD gene. 198 61

Data from differential scanning calorimetry (DSC) may be used to estimate very large binding constants that cannot be conveniently measured by more conventional equilibrium techniques. Thermodynamic models have been formulated to describe interacting systems that involve either one thermal transition (protein-ligand) or two thermal transitions (protein-protein) and either 1:1 or higher binding stoichiometry. Methods are described for obtaining binding constants and heats of binding by two different methods: calculation or simulation fitting of data. Extensive DSC data on 2'CMP binding to RNase are presented and analyzed by the two methods. It is found that the methods agree when binding sites are completely saturated, but substantial errors arise in the calculation method when site saturation is incomplete and the transition of liganded molecules overlaps that of unliganded molecules. This arises primarily from an inability to determine TM (i.e., the temperature where concentrations of folded and unfolded protein are equal) under weak-binding conditions. Results from simulation show that the binding constants and heats of binding from the DSC method agree quantitatively with corresponding estimates obtained from equilibrium methods when extrapolated to the same temperature. It was also found from the DSC data that the binding constant decreases with increasing concentration of ligand, which might arise from nonideality effects associated with dimerization of 2'CMP. Simulations show that the DSC method is capable of estimating binding constants for ultratight interactions up to perhaps 10(40) M-1 or higher, while most equilibrium methods fail well below 10(10) M-1. DSC data from the literature on a number of interacting systems (trypsin-soybean trypsin inhibitor, trypsin-ovomucoid, trypsin-pancreatic trypsin inhibitor, chymotrypsin-subtilisin inhibitor, subtilisin BPN-subtilisin inhibitor, RNase S protein-RNase S peptide, avidin-biotin, ovotransferrin-Fe3+, superoxide dismutase-Zn2+, alkaline phosphatase-Zn2+, and assembly of regulatory and catalytic subunits of aspartate transcarbamoylase) were analyzed by simulation fitting or by calculation. Apparent single-site binding constants ranged from ca. 10(5) to 10(20) M-1, while the interaction constant for assembly of aspartate transcarbamoylase was estimated as 10(37) in molarity units. For most of these systems, the DSC interaction constants compared favorably with other literature estimates, for some it did not for reasons unknown, while for still others this represented the first estimate. Simulations show that for proteins having two binding sites for the same ligand within a single cooperative unit, ligand rearrangement will occur spontaneously during a DSC scan as the transition temperature of the unliganded protein is approached.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Study of strong to ultratight protein interactions using differential scanning calorimetry. 220 24

Three regulatory proteins are involved in the post-transcriptional control of arginine metabolism in Saccharomyces cerevisiae: ARGRI, ARGRII and ARGRIII. The 880 amino acid ARGRII protein, like some DNA binding proteins, possesses in its N-terminal sequence a cysteine-rich region that presents homology to the zinc binding region of Escherichia coli aspartate transcarbamylase. ARGRII also has a region of 90 amino acids that is 30% homologous to the E. coli ARGR repressor. Moreover a 87 amino acid long sequence of ARGRII contains three stretches with significant homology to some viral, bacterial and pancreatic RNases. We propose a model in which the RNase-like sequence could regulate the expression of arginine anabolic messenger RNAs.
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PMID:The yeast ARGRII regulatory protein has homology with various RNases and DNA binding proteins. 312 9