Structural and functional studies of the human phosphoribosyltransferase domain containing protein 1.
Human hypoxanthine-guanine phosphoribosyltransferase (HPRT) (EC 2.4.2.8) catalyzes the conversion of hypoxanthine and guanine to their respective nucleoside monophosphates. Human HPRT deficiency as a result of genetic mutations is linked to both Lesch-Nyhan disease and gout. In the present study, we have characterized phosphoribosyltransferase domain containing protein 1 (PRTFDC1), a human HPRT homolog of unknown function. The PRTFDC1 structure has been determined at 1.7 Å resolution with bound GMP. The overall structure and GMP binding mode are very similar to that observed for HPRT. Using a thermal-melt assay, a nucleotide metabolome library was screened against PRTFDC1 and revealed that hypoxanthine and guanine specifically interacted with the enzyme. It was subsequently confirmed that PRTFDC1 could convert these two bases into their corresponding nucleoside monophosphate. However, the catalytic efficiency (k(cat)/K(m)) of PRTFDC1 towards hypoxanthine and guanine was only 0.26% and 0.09%, respectively, of that of HPRT. This low activity could be explained by the fact that PRTFDC1 has a Gly in the position of the proposed catalytic Asp of HPRT. In PRTFDC1, a water molecule at the position of the aspartic acid side chain position in HPRT might be responsible for the low activity observed by acting as a weak base. The data obtained in the present study indicate that PRTFDC1 does not have a direct catalytic role in the nucleotide salvage pathway.
Structural Genomics Consortium, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
Martin
M
Welin
Louise
L
Egeblad
Andreas
A
Johansson
Pål
P
Stenmark
Liya
L
Wang
Susanne
S
Flodin
Tomas
T
Nyman
Lionel
L
Trésaugues
Tetyana
T
Kotenyova
Ida
I
Johansson
Staffan
S
Eriksson
Hans
H
Eklund
Pär
P
Nordlund
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D006147:Guanine / Q000378:metabolism; D006157:Guanosine Monophosphate / Q000378:metabolism; D006801:Humans; D019271:Hypoxanthine / Q000378:metabolism; D007041:Hypoxanthine Phosphoribosyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D055442:Metabolome; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D040681:Structural Homology, Protein; D013379:Substrate Specificity
D019271:Hypoxanthine; D006147:Guanine; D006157:Guanosine Monophosphate; D007041:Hypoxanthine Phosphoribosyltransferase; C554253:PRTFDC1 protein, human