2xak

From Proteopedia

(Redirected from 2x0z)

Ribonucleotide reductase Y730NO2Y modified R1 subunit of E. coli

Structural highlights

2xak is a 7 chain structure with sequence from Escherichia coli K-12. This structure supersedes the now removed PDB entry 2x0z. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2.8Å
Ligands:
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

RIR1_ECOLI Provides the precursors necessary for DNA synthesis. Catalyzes the biosynthesis of deoxyribonucleotides from the corresponding ribonucleotides. R1 contains the binding sites for both substrates and allosteric effectors and carries out the actual reduction of the ribonucleotide. It also provides redox-active cysteines.

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

Publication Abstract from PubMed

E. coli ribonucleotide reductase catalyzes the reduction of nucleoside 5'-diphosphates into 2'-deoxynucleotides and is composed of two subunits: alpha2 and beta2. During turnover, a stable tyrosyl radical (Y*) at Y(122)-beta2 reversibly oxidizes C(439) in the active site of alpha2. This radical propagation step is proposed to occur over 35 A, to use specific redox-active tyrosines (Y(122) and Y(356) in beta2, Y(731) and Y(730) in alpha2), and to involve proton-coupled electron transfer (PCET). 3-Nitrotyrosine (NO(2)Y, pK(a) 7.1) has been incorporated in place of Y(122), Y(731), and Y(730) to probe how the protein environment perturbs each pK(a) in the presence of the second subunit, substrate (S), and allosteric effector (E). The activity of each mutant is <4 x 10(-3) that of the wild-type (wt) subunit. The [NO(2)Y(730)]-alpha2 and [NO(2)Y(731)]-alpha2 each exhibit a pK(a) of 7.8-8.0 with E and E/beta2. The pK(a) of [NO(2)Y(730)]-alpha2 is elevated to 8.2-8.3 in the S/E/beta2 complex, whereas no further perturbation is observed for [NO(2)Y(731)]-alpha2. Mutations in pathway residues adjacent to the NO(2)Y that disrupt H-bonding minimally perturb its pK(a). The pK(a) of NO(2)Y(122)-beta2 alone or with alpha2/S/E is >9.6. X-ray crystal structures have been obtained for all [NO(2)Y]-alpha2 mutants (2.1-3.1 A resolution), which show minimal structural perturbation compared to wt-alpha2. Together with the pK(a) of the previously reported NO(2)Y(356)-beta2 (7.5 in the alpha2/S/E complex; Yee, C. et al. Biochemistry 2003, 42, 14541-14552), these studies provide a picture of the protein environment of the ground state at each Y in the PCET pathway, and are the starting point for understanding differences in PCET mechanisms at each residue in the pathway.

Site-Specific Incorporation of 3-Nitrotyrosine as a Probe of pK(a) Perturbation of Redox-Active Tyrosines in Ribonucleotide Reductase.,Yokoyama K, Uhlin U, Stubbe J J Am Chem Soc. 2010 Jun 2. PMID:20518462^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Yokoyama K, Uhlin U, Stubbe J. Site-Specific Incorporation of 3-Nitrotyrosine as a Probe of pK(a) Perturbation of Redox-Active Tyrosines in Ribonucleotide Reductase. J Am Chem Soc. 2010 Jun 2. PMID:20518462 doi:10.1021/ja101097p