Abstract
Background: Histamine plays important biological roles in cell-to-cell communication; it is a mediator in allergic responses, a regulator of gastric acid secretion, a messenger in bronchial asthma, and a neurotransmitter in the central nervous system. Histamine acts by binding to histamine receptors, and its local action is terminated primarily by methylation. Human histamine N-methyltransferase (HNMT) has a common polymorphism at residue 105 that correlates with the high- (Thr) and low- (Ile) activity phenotypes. Results: Two ternary structures of human HNMT have been determined: the Thr105 variant complexed with its substrate histamine and reaction product AdoHcy and the Ile105 variant complexed with an inhibitor (quinacrine) and AdoHcy. Our steady-state kinetic data indicate that the recombinant Ile105 variant shows 1.8- and 1.3-fold increases in the apparent KM for AdoMet and histamine, respectively, and slightly (16%) but consistently lower specific activity as compared to that of the Thr105 variant. These differences hold over a temperature range of 25°C-45°C in vitro. Only at a temperature of 50°C or higher is the Ile105 variant more thermolabile than the Thr105 enzyme. Conclusions: HNMT has a 2 domain structure including a consensus AdoMet binding domain, where the residue 105 is located on the surface, consistent with the kinetic data that the polymorphism does not affect overall protein stability at physiological temperatures but lowers KM values for AdoMet and histamine. The interactions between HNMT and quinacrine provide the first structural insights into a large group of pharmacologic HNMT inhibitors and their mechanisms of inhibition.
| Original language | English |
|---|---|
| Pages (from-to) | 837-849 |
| Number of pages | 13 |
| Journal | Structure |
| Volume | 9 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - 2001 |
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Keywords
- Antimalarial drug quinacrine
- Histamine
- Methylation
- Polymorphism
- Thermal stability
ASJC Scopus subject areas
- Molecular Biology
- Structural Biology
Cite this
Two polymorphic forms of human histamine methyltransferase : Structural, thermal, and kinetic comparisons. / Horton, John R.; Sawada, Ken; Nishibori, Masahiro; Zhang, Xing; Cheng, Xiaodong.
In: Structure, Vol. 9, No. 9, 2001, p. 837-849.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Two polymorphic forms of human histamine methyltransferase
T2 - Structural, thermal, and kinetic comparisons
AU - Horton, John R.
AU - Sawada, Ken
AU - Nishibori, Masahiro
AU - Zhang, Xing
AU - Cheng, Xiaodong
PY - 2001
Y1 - 2001
N2 - Background: Histamine plays important biological roles in cell-to-cell communication; it is a mediator in allergic responses, a regulator of gastric acid secretion, a messenger in bronchial asthma, and a neurotransmitter in the central nervous system. Histamine acts by binding to histamine receptors, and its local action is terminated primarily by methylation. Human histamine N-methyltransferase (HNMT) has a common polymorphism at residue 105 that correlates with the high- (Thr) and low- (Ile) activity phenotypes. Results: Two ternary structures of human HNMT have been determined: the Thr105 variant complexed with its substrate histamine and reaction product AdoHcy and the Ile105 variant complexed with an inhibitor (quinacrine) and AdoHcy. Our steady-state kinetic data indicate that the recombinant Ile105 variant shows 1.8- and 1.3-fold increases in the apparent KM for AdoMet and histamine, respectively, and slightly (16%) but consistently lower specific activity as compared to that of the Thr105 variant. These differences hold over a temperature range of 25°C-45°C in vitro. Only at a temperature of 50°C or higher is the Ile105 variant more thermolabile than the Thr105 enzyme. Conclusions: HNMT has a 2 domain structure including a consensus AdoMet binding domain, where the residue 105 is located on the surface, consistent with the kinetic data that the polymorphism does not affect overall protein stability at physiological temperatures but lowers KM values for AdoMet and histamine. The interactions between HNMT and quinacrine provide the first structural insights into a large group of pharmacologic HNMT inhibitors and their mechanisms of inhibition.
AB - Background: Histamine plays important biological roles in cell-to-cell communication; it is a mediator in allergic responses, a regulator of gastric acid secretion, a messenger in bronchial asthma, and a neurotransmitter in the central nervous system. Histamine acts by binding to histamine receptors, and its local action is terminated primarily by methylation. Human histamine N-methyltransferase (HNMT) has a common polymorphism at residue 105 that correlates with the high- (Thr) and low- (Ile) activity phenotypes. Results: Two ternary structures of human HNMT have been determined: the Thr105 variant complexed with its substrate histamine and reaction product AdoHcy and the Ile105 variant complexed with an inhibitor (quinacrine) and AdoHcy. Our steady-state kinetic data indicate that the recombinant Ile105 variant shows 1.8- and 1.3-fold increases in the apparent KM for AdoMet and histamine, respectively, and slightly (16%) but consistently lower specific activity as compared to that of the Thr105 variant. These differences hold over a temperature range of 25°C-45°C in vitro. Only at a temperature of 50°C or higher is the Ile105 variant more thermolabile than the Thr105 enzyme. Conclusions: HNMT has a 2 domain structure including a consensus AdoMet binding domain, where the residue 105 is located on the surface, consistent with the kinetic data that the polymorphism does not affect overall protein stability at physiological temperatures but lowers KM values for AdoMet and histamine. The interactions between HNMT and quinacrine provide the first structural insights into a large group of pharmacologic HNMT inhibitors and their mechanisms of inhibition.
KW - Antimalarial drug quinacrine
KW - Histamine
KW - Methylation
KW - Polymorphism
KW - Thermal stability
UR - http://www.scopus.com/inward/record.url?scp=0034812118&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034812118&partnerID=8YFLogxK
U2 - 10.1016/S0969-2126(01)00643-8
DO - 10.1016/S0969-2126(01)00643-8
M3 - Article
C2 - 11566133
AN - SCOPUS:0034812118
VL - 9
SP - 837
EP - 849
JO - Structure with Folding & design
JF - Structure with Folding & design
SN - 0969-2126
IS - 9
ER -