Solution structure of the MutT enzyme, a nucleoside triphosphate pyrophosphohydrolase.
The MutT enzyme (129 residues) catalyzes the hydrolysis of normal and mutagenic nucleoside triphosphates, such as 8-oxo-dGTP, by substitution at the rarely attacked beta-P, to yield NMP and pyrophosphate. Previous heteronuclear NMR studies of MutT have shown the secondary structure to consist of a five-stranded mixed beta-sheet connected by the loop I-alpha-helix I--loop II motif, by two tight turns, and by loop III, and terminated by loop IV--alpha-helix II [Abeygunawardana et al. (1993) Biochemistry 32, 13071-13080; Weber et al. (1993) Biochemistry 32, 13081-13087). Complete side-chain assignments of 1H and 13C resonances have now been made by 3D C(CO)NH and HCCH-TOCSY experiments. A total of 1461 interproton proximities (11 per residue), obtained by 3D 15N-resolved NOESY-HSQC and 3D 13C-resolved NOESY-HSQC spectra, including 372 long-range NOEs, as well as 65 dihedral angle (phi) restraints and 34 backbone hydrogen bond restraints were used to determine the tertiary structure of MutT by distance geometry, simulated annealing, and energy minimization with the program X-PLOR. The structure is globular and compact with the parallel portion of the beta-sheet sandwiched between the two alpha-helices, forming an alpha+beta fold. The essential divalent cation has previously been shown to bind near residues Gly-37, Gly-38, Lys-39, and Glu-57, and nucleotides have been shown to bind near residues Leu-54 and Val-58 by NMR relaxation methods [Frick et al. (1995) Biochemistry 34, 5577-5586].(ABSTRACT TRUNCATED AT 250 WORDS)
Abeygunawardana
C
C
Department of Biological Chemistry, Johns Hopkins School of Medicine, Baltimore, Maryland 21205-2185, USA.
Weber
D J
DJ
Gittis
A G
AG
Frick
D N
DN
Lin
J
J
Miller
A F
AF
Bessman
M J
MJ
Mildvan
A S
AS
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003848:Deoxyguanine Nucleotides / Q000378:metabolism; D004563:Electrochemistry; D029968:Escherichia coli Proteins; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011755:Pyrophosphatases; D012996:Solutions
D001426:Bacterial Proteins; D003848:Deoxyguanine Nucleotides; D029968:Escherichia coli Proteins; D012996:Solutions; C078206:8-oxodeoxyguanosine triphosphate; D011392:Proline; D010744:Phosphoric Monoester Hydrolases; D011755:Pyrophosphatases; C052211:mutT protein, E coli