PMID- 10338013
OWN - NLM
STAT- MEDLINE
DCOM- 19990811
LR  - 20181113
IS  - 0961-8368 (Print)
IS  - 0961-8368 (Linking)
VI  - 8
IP  - 5
DP  - 1999 May
TI  - Ternary complex structure of human HGPRTase, PRPP, Mg2+, and the inhibitor HPP
      reveals the involvement of the flexible loop in substrate binding.
PG  - 1023-31
AB  - Site-directed mutagenesis was used to replace Lys68 of the human hypoxanthine
      phosphoribosyltransferase (HGPRTase) with alanine to exploit this less reactive
      form of the enzyme to gain additional insights into the structure activity
      relationship of HGPRTase. Although this substitution resulted in only a minimal
      (one- to threefold) increase in the Km values for binding pyrophosphate or
      phosphoribosylpyrophosphate, the catalytic efficiencies (k(cat)/Km) of the
      forward and reverse reactions were more severely reduced (6- to 30-fold), and the
      mutant enzyme showed positive cooperativity in binding of
      alpha-D-5-phosphoribosyl-1-pyrophosphate (PRPP) and nucleotide. The K68A form of 
      the human HGPRTase was cocrystallized with 7-hydroxy [4,3-d] pyrazolo pyrimidine 
      (HPP) and Mg PRPP, and the refined structure reported. The PRPP molecule built
      into the [(Fo - Fc)phi(calc)] electron density shows atomic interactions between 
      the Mg PRPP and enzyme residues in the pyrophosphate binding domain as well as in
      a long flexible loop (residues Leu101 to Gly111) that closes over the active
      site. Loop closure reveals the functional roles for the conserved SY dipeptide of
      the loop as well as the molecular basis for one form of gouty arthritis (S103R). 
      In addition, the closed loop conformation provides structural information
      relevant to the mechanism of catalysis in human HGPRTase.
FAU - Balendiran, G K
AU  - Balendiran GK
AD  - Department of Biochemistry and Biophysics, Texas A&M University, College Station 
      77843-2128, USA. balendra@reddrum.tamu.edu
FAU - Molina, J A
AU  - Molina JA
FAU - Xu, Y
AU  - Xu Y
FAU - Torres-Martinez, J
AU  - Torres-Martinez J
FAU - Stevens, R
AU  - Stevens R
FAU - Focia, P J
AU  - Focia PJ
FAU - Eakin, A E
AU  - Eakin AE
FAU - Sacchettini, J C
AU  - Sacchettini JC
FAU - Craig, S P 3rd
AU  - Craig SP 3rd
LA  - eng
GR  - AI-34326/AI/NIAID NIH HHS/United States
GR  - AI-38919/AI/NIAID NIH HHS/United States
GR  - GM-52125/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Protein Sci
JT  - Protein science : a publication of the Protein Society
JID - 9211750
RN  - 0 (7-hydroxy(4,3-d)pyrazolo pyrimidine)
RN  - 0 (Pyrazoles)
RN  - 0 (Pyrimidines)
RN  - 7540-64-9 (Phosphoribosyl Pyrophosphate)
RN  - EC 2.4.2.8 (Hypoxanthine Phosphoribosyltransferase)
RN  - I38ZP9992A (Magnesium)
SB  - IM
MH  - Animals
MH  - Crystallography, X-Ray
MH  - Humans
MH  - Hypoxanthine Phosphoribosyltransferase/*chemistry
MH  - Kinetics
MH  - Magnesium/*chemistry
MH  - Models, Molecular
MH  - Mutagenesis, Site-Directed
MH  - Phosphoribosyl Pyrophosphate/*chemistry
MH  - Protein Binding
MH  - Pyrazoles/*chemistry
MH  - Pyrimidines/*chemistry
MH  - Time Factors
MH  - Trypanosoma cruzi/enzymology
PMC - PMC2144341
EDAT- 1999/05/25 06:00
MHDA- 2001/03/28 10:01
CRDT- 1999/05/25 06:00
PHST- 1999/05/25 06:00 [pubmed]
PHST- 2001/03/28 10:01 [medline]
PHST- 1999/05/25 06:00 [entrez]
AID - 10.1110/ps.8.5.1023 [doi]
PST - ppublish
SO  - Protein Sci. 1999 May;8(5):1023-31. doi: 10.1110/ps.8.5.1023.