1non

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spinqualitylabelsall models 1non, resolution 2.40Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

PyrR, the regulator of the pyrimidine biosynthetic operon in Bacillus caldolyticus

Overview

PyrR is a protein that regulates the expression of genes and operons of, pyrimidine nucleotide biosynthesis (pyr genes) in many bacteria. PyrR acts, by binding to specific sequences on pyr mRNA and causing transcriptional, attenuation when intracellular levels of uridine nucleotides are elevated., PyrR from Bacillus subtilis has been purified and extensively studied. In, this work, we describe the purification to homogeneity and, characterization of recombinant PyrR from the thermophile Bacillus, caldolyticus and the crystal structures of unliganded PyrR and a, PyrR-nucleotide complex. The B. caldolyticus pyrR gene was previously, shown to restore normal regulation of the B. subtilis pyr operon in a pyrR, deletion mutant. Like B. subtilis PyrR, B. caldolyticus PyrR catalyzes the, uracil phosphoribosyltransferase reaction but with maximal activity at 60, degrees C. Crystal structures of B. caldolyticus PyrR reveal a dimer, similar to the B. subtilis PyrR dimer and, for the first time, binding, sites for nucleotides. UMP and GMP, accompanied by Mg2+, bind specifically, to PyrR active sites. Nucleotide binding to PyrR is similar to other, phosphoribosyltransferases, but Mg2+ binding differs. GMP binding was, unexpected. The protein bound specific sequences of pyr RNA 100 to 1,000, times more tightly than B. subtilis PyrR, depending on the RNA tested and, the assay method; uridine nucleotides enhanced RNA binding, but guanosine, nucleotides antagonized it. The new findings of specific GMP binding and, its antagonism of RNA binding suggest cross-regulation of the pyr operon, by purines.

About this Structure

1NON is a Single protein structure of sequence from Bacillus caldolyticus. Active as Uracil phosphoribosyltransferase, with EC number 2.4.2.9 Full crystallographic information is available from OCA.

Reference

Structure of the nucleotide complex of PyrR, the pyr attenuation protein from Bacillus caldolyticus, suggests dual regulation by pyrimidine and purine nucleotides., Chander P, Halbig KM, Miller JK, Fields CJ, Bonner HK, Grabner GK, Switzer RL, Smith JL, J Bacteriol. 2005 Mar;187(5):1773-82. PMID:15716449

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