A naturally occurring 46-amino acid deletion of cytidine monophospho-N-acetylneuraminic acid hydroxylase leads to a change in the intracellular distribution of the protein.
Cytidine monophospho-N-acetylneuraminic acid (CMP-NeuAc) hydroxylase is a key enzyme for the expression of N-glycolylneuraminic acid. The molecular cloning of this enzyme from mouse liver has been described in our previous report (Kawano T, Koyama S, Takematsu H, Kozutsumi Y, Kawasaki H, Kawashima S, Kawasaki T, Suzuki A (1995) J Biol Chem 270: 16458-63). During the cDNA cloning, a cDNA containing a truncated open reading frame (ORF) was isolated. This clone encodes a protein of 531 amino acids which lacks 46 amino acids in the middle of the normal full-length protein. The percentage of this mRNA containing the truncated ORF out of the total population of CMP-NeuAc hydroxylase mRNA in various mouse tissues was about 10-25%. The truncated protein was expressed in COS-1 cells, but did not show any enzymatic activity. The truncated protein was localized to the region which appeared to be the endoplasmic reticulum, whereas the full-length protein with normal enzymatic activity was detected in the cytosol. These data suggest that this naturally occurring 46-amino acid deletion leads to a change in the intracellular distribution of CMP-NeuAc hydroxylase, and a loss in the activity of this enzyme.
Koyama
S
S
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
Yamaji
T
T
Takematsu
H
H
Kawano
T
T
Kozutsumi
Y
Y
Suzuki
A
A
Kawasaki
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D017931:DNA Primers; D019084:Fluorescent Antibody Technique, Indirect; D008099:Liver / Q000201:enzymology; D051379:Mice; D006899:Mixed Function Oxygenases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis; D017384:Sequence Deletion; D013347:Subcellular Fractions / Q000201:enzymology; D014162:Transfection
D017931:DNA Primers; D011994:Recombinant Proteins; D006899:Mixed Function Oxygenases; C074383:CMPacetylneuraminate monooxygenase