1zdr
From Proteopedia
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[[Image:1zdr.gif|left|200px]] | [[Image:1zdr.gif|left|200px]] | ||
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'''DHFR from Bacillus Stearothermophilus''' | '''DHFR from Bacillus Stearothermophilus''' | ||
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==About this Structure== | ==About this Structure== | ||
| - | + | Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ZDR OCA]. | |
==Reference== | ==Reference== | ||
Structure and hydride transfer mechanism of a moderate thermophilic dihydrofolate reductase from Bacillus stearothermophilus and comparison to its mesophilic and hyperthermophilic homologues., Kim HS, Damo SM, Lee SY, Wemmer D, Klinman JP, Biochemistry. 2005 Aug 30;44(34):11428-39. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/16114879 16114879] | Structure and hydride transfer mechanism of a moderate thermophilic dihydrofolate reductase from Bacillus stearothermophilus and comparison to its mesophilic and hyperthermophilic homologues., Kim HS, Damo SM, Lee SY, Wemmer D, Klinman JP, Biochemistry. 2005 Aug 30;44(34):11428-39. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/16114879 16114879] | ||
[[Category: Dihydrofolate reductase]] | [[Category: Dihydrofolate reductase]] | ||
| - | [[Category: Geobacillus stearothermophilus]] | ||
| - | [[Category: Protein complex]] | ||
[[Category: Damo, S M.]] | [[Category: Damo, S M.]] | ||
[[Category: Kim, H S.]] | [[Category: Kim, H S.]] | ||
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[[Category: Lee, S Y.]] | [[Category: Lee, S Y.]] | ||
[[Category: Wemmer, D.]] | [[Category: Wemmer, D.]] | ||
| - | [[Category: | + | [[Category: Dhfr]] |
| - | [[Category: | + | [[Category: Nadp]] |
| - | [[Category: | + | [[Category: Oxidoreductase]] |
| - | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 17:30:18 2008'' | |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | |
Revision as of 14:30, 3 May 2008
DHFR from Bacillus Stearothermophilus
Overview
Dihydrofolate reductase (DHFR) from a moderate thermophilic organism, Bacillus stearothermophilus, has been cloned and expressed. Physical characterization of the protein (BsDHFR) indicates that it is a monomeric protein with a molecular mass of 18,694.6 Da (0.8), coincident with the mass of 18 694.67 Da calculated from the primary sequence. Determination of the X-ray structure of BsDHFR provides the first structure for a monomeric DHFR from a thermophilic organism, indicating a high degree of conservation of structure in relation to all chromosomal DHFRs. Structurally based sequence alignment of DHFRs indicates the following levels of sequence identity and similarity for BsDHFR: 38 and 58% with Escherichia coli, 35 and 56% with Lactobacillus casei, and 23 and 40% with Thermotoga maritima, respectively. Steady state kinetic isotope effect studies indicate an ordered kinetic mechanism at elevated temperatures, with NADPH binding first to the enzyme. This converts to a more random mechanism at reduced temperatures, reflected in a greatly reduced K(m) for dihydrofolate at 20 degrees C in relation to that at 60 degrees C. A reduction in either temperature or pH reduces the degree to which the hydride transfer step is rate-determining for the second-order reaction of DHF with the enzyme-NADPH binary complex. Transient state kinetics have been used to study the temperature dependence of the isotope effect on hydride transfer at pH 9 between 10 and 50 degrees C. The data support rate-limiting hydride transfer with a moderate enthalpy of activation (E(a) = 5.5 kcal/mol) and a somewhat greater temperature dependence for the kinetic isotope effect than predicted from classical behavior [A(H)/A(D) = 0.57 (0.15)]. Comparison of kinetic parameters for BsDHFR to published data for DHFR from E. coli and T. maritima shows a decreasing trend in efficiency of hydride transfer with increasing thermophilicity of the protein. These results are discussed in the context of the capacity of each enzyme to optimize H-tunneling from donor (NADPH) to acceptor (DHF) substrates.
About this Structure
Full crystallographic information is available from OCA.
Reference
Structure and hydride transfer mechanism of a moderate thermophilic dihydrofolate reductase from Bacillus stearothermophilus and comparison to its mesophilic and hyperthermophilic homologues., Kim HS, Damo SM, Lee SY, Wemmer D, Klinman JP, Biochemistry. 2005 Aug 30;44(34):11428-39. PMID:16114879 Page seeded by OCA on Sat May 3 17:30:18 2008
