Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 278, Issue 29, Pages 26722-26726Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M303774200
Keywords
-
Categories
Funding
- NIDDK NIH HHS [DK54423] Funding Source: Medline
Ask authors/readers for more resources
Depending on their physiological role, carbamoyl phosphate synthetases (CPSs) use either glutamine or free ammonia as the nitrogen donor for carbamoyl phosphate synthesis. Sequence analysis of known CPSs indicates that, regardless of whether they are ammonia- or glutamine-specific, all CPSs contain the structural equivalent of a triad-type glutamine amidotransferase ( GAT) domain. In ammonia- specific CPSs, such as those of rat or human, the catalytic inactivity of the GAT domain can be rationalized by the substitution of the Triad cysteine residue by serine (1). The ammonia- specific CPS of Rana catesbeiana (fCPS) presents an interesting anomaly in that, despite its retention of the entire catalytic triad (2) and almost all other residues conserved in Triad GATs, it is unable to utilize glutamine as a nitrogen-donating substrate (3). Based on our earlier work with the glutamine-utilizing E. coli CPS (eCPS), we have targeted residues Lys(258) and Glu(261) in the fCPS GAT domain as critical for preventing GAT function. Previously we have shown that substitution of the corresponding residues in eCPS by their fCPS counterparts (Leu --> Lys and Gln --> Glu) resulted in complete loss of GAT function in eCPS (3). To examine the role of these residues in the fCPS GAT component, we have cloned the full-length fCPS gene from R. catesbeiana liver. Here we report the first heterologous expression of an ammonia- specific CPS and show that a single mutation of the frog enzyme, K258L, yields a gain of glutaminase function.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available