Search

No abstract.

The crystal structure of YecO from Haemophilus influenzae(HI0319), a protein annotated in the sequence databases as hypothetical, and that has not been assigned a function, has been determined at 2.2‐Å resolution. The structure reveals a fold typical of S‐adenosyl‐L‐methionine‐dependent (AdoMet) methyltransferase enzymes. Moreover, a processed cofactor, S‐adenosyl‐L‐homocysteine (AdoHcy), is bound to the enzyme, further confirming the biochemical function of HI0319 and its sequence family members. An active site arginine, shielded from bulk solvent, interacts with an anion, possibly a chloride ion, which in turn interacts with the sulfur atom of AdoHcy. The AdoHcy and nearby protein residues delineate a small solvent‐excluded substrate binding cavity of 162 Å3in volume. The environment surrounding the cavity indicates that the substrate molecule contains a hydrophobic moiety and an anionic group. Many of the residues that define the cavity are invariant in the HI0319 sequence family but are not conserved in other methyltransferases. Therefore, the substrate specificity of YecO enzymes is unique and differs from the substrate specificity of all other methyltransferases sequenced to date. Examination of the Enzyme Commission list of methyltransferases prompted a manual inspection of 10 possible substrates using computer graphics and suggested that the ortho‐substituted benzoic acids fit best in the active site. Proteins 2001;45:397–407. © 2001 Wiley‐Liss, Inc.

The crystal structure of YecO from Haemophilus influenzae (HI0319), a protein annotated in the sequence databases as hypothetical, and that has not been assigned a function, has been determined at 2.2-Å resolution. The structure reveals a fold typical of S-adenosyl-L-methionine-dependent (AdoMet) methyltransferase enzymes. Moreover, a processed cofactor, S-adenosyl-L-homocysteine (AdoHcy), is bound to the enzyme, further confirming the biochemical function of HI0319 and its sequence family members. An active site arginine, shielded from bulk solvent, interacts with an anion, possibly a chloride ion, which in turn interacts with the sulfur atom of AdoHcy. The AdoHcy and nearby protein residues delineate a small solvent-excluded substrate binding cavity of 162 ų in volume. The environment surrounding the cavity indicates that the substrate molecule contains a hydrophobic moiety and an anionic group. Many of the residues that define the cavity are invariant in the HI0319 sequence family but are not conserved in other methyltransferases. Therefore, the substrate specificity of YecO enzymes is unique and differs from the substrate specificity of all other methyltransferases sequenced to date. Examination of the Enzyme Commission list of methyltransferases prompted a manual inspection of 10 possible substrates using computer graphics and suggested that the ortho-substituted benzoic acids fit best in the active site. Proteins 2001;45:397–407. © 2001 Wiley-Liss, Inc.

The crystal structure of cobalt-substituted azurin from Pseudomonas aeruginosa has been determined to final crystallographic R value of 0.175 at 1.9 Å resolution. There are four molecules in the asymmetric unit in the structure, and these four molecules are packed as a dimer of dimers. The dimer packing is very similar to that of the wild-type Pseudomonas aeruginosa azurin dimer. Replacement of the native copper by the cobalt ion has only small effects on the metal binding site presumably because of the existence of an extensive network of hydrogen bonds in its immediate neighborhood. Some differences are obvious, however. In wild-type azurin the copper atom occupies a distorted trigonal bipyramidal site, while cobalt similar to zinc and nickel occupy a distorted tetrahedral site, in which the distance to the Met121,S^δ atom is increased to 3.3–3.5 Å and the distance to the carbonyl oxygen of Gly45 has decreased to 2.1–2.4 Å. The X-band EPR spectrum of the high-spin Co(II) in azurin is well resolved (apparent g values gx' = 5.23; gy' = 3.83; gz' = 1.995, and hyperfine splittings Ax' = 31; Ay' = 20–30; Az' = 53 G) and indicates that the ligand field is close to axial. Proteins 27:385–394, 1997. © 1997 Wiley-Liss, Inc.