TY - JOUR
T1 - The molecular basis of ornithine transcarbamylase deficiency
T2 - Modelling the human enzyme and the effects of mutations
AU - Tuchman, Mendel
AU - Morizono, Hiroki
AU - Reish, Orit
AU - Yuan, Xiaoling
AU - Allewell, Norma M.
PY - 1995
Y1 - 1995
N2 - Human ornithine transcarbamylase is a trimer with 46% amino acid sequence homology to the catalytic subunit of Ecoli aspartate transcarbamylase. Secondary structure predictions, distributions of hydrophilic and hydrophobic regions, and the pattern of conserved residues suggest that the three dimensional structures of the two proteins are likely to be similar. A three dimensional model of ornithine transcarbamylase was generated from the crystal structure of the catalytic subunit of Ecoli aspartate transcarbamylase in the holoenzyme, by aligning the sequences, building in gaps, and minimising the energy. The binding sites for carbamyl phosphate in both enzymes are similar and the ornithine binding site in ornithine transcarbamylase appears to be in the same location as the L-aspartate binding site in aspartate transcarbamylase, with negatively charged side chains replaced by positively charged residues. Mutations in the ornithine transcarbamylase gene found in patients with hyperammonaemia of the "neonatal type" are clustered in important structural or functional domains, either in the interior of the protein, at the active site, or at the interchain interface, while mutations found in patients with milder "late onset" disease are located primarily on the surface of the protein. The predicted effects of all known missense mutations and in frame deletions in the ornithine transcarbamylase gene on the structure and function of the mature enzyme are described.
AB - Human ornithine transcarbamylase is a trimer with 46% amino acid sequence homology to the catalytic subunit of Ecoli aspartate transcarbamylase. Secondary structure predictions, distributions of hydrophilic and hydrophobic regions, and the pattern of conserved residues suggest that the three dimensional structures of the two proteins are likely to be similar. A three dimensional model of ornithine transcarbamylase was generated from the crystal structure of the catalytic subunit of Ecoli aspartate transcarbamylase in the holoenzyme, by aligning the sequences, building in gaps, and minimising the energy. The binding sites for carbamyl phosphate in both enzymes are similar and the ornithine binding site in ornithine transcarbamylase appears to be in the same location as the L-aspartate binding site in aspartate transcarbamylase, with negatively charged side chains replaced by positively charged residues. Mutations in the ornithine transcarbamylase gene found in patients with hyperammonaemia of the "neonatal type" are clustered in important structural or functional domains, either in the interior of the protein, at the active site, or at the interchain interface, while mutations found in patients with milder "late onset" disease are located primarily on the surface of the protein. The predicted effects of all known missense mutations and in frame deletions in the ornithine transcarbamylase gene on the structure and function of the mature enzyme are described.
UR - http://www.scopus.com/inward/record.url?scp=0029052816&partnerID=8YFLogxK
U2 - 10.1136/jmg.32.9.680
DO - 10.1136/jmg.32.9.680
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C2 - 8544185
AN - SCOPUS:0029052816
SN - 0022-2593
VL - 32
SP - 680
EP - 688
JO - Journal of Medical Genetics
JF - Journal of Medical Genetics
IS - 9
ER -