4LA5

Crystal structure of 2-methylisoborneol synthase from Streptomyces coelicolor A3(2)

Summary for 4LA5

• Entry DOI: 10.2210/pdb4la5/pdb
• Related: 3V1V 3V1X 4LA6
• Descriptor: 2-methylisoborneol synthase (2 entities in total)
• Functional Keywords: terpenoid biosynthesis, biosynthesis, isoprenoid synthase fold, lyase
• Biological source: Streptomyces coelicolor
• Total number of polymer chains: 1
• Total formula weight: 50144.90

Authors

Koksal, M.,Christianson, D.W. (deposition date: 2013-06-19, release date: 2013-07-31, Last modification date: 2023-09-20)

Primary citation

Koksal, M.,Chou, W.K.,Cane, D.E.,Christianson, D.W.
Unexpected reactivity of 2-fluorolinalyl diphosphate in the active site of crystalline 2-methylisoborneol synthase.
Biochemistry, 52:5247-5255, 2013

PubMed Abstract: The crystal structure of 2-methylisoborneol synthase (MIBS) from Streptomyces coelicolor A3(2) has been determined in its unliganded state and in complex with two Mg(2+) ions and 2-fluoroneryl diphosphate at 1.85 and 2.00 Å resolution, respectively. Under normal circumstances, MIBS catalyzes the cyclization of the naturally occurring, noncanonical 11-carbon isoprenoid substrate, 2-methylgeranyl diphosphate, which first undergoes an ionization-isomerization-ionization sequence through the tertiary diphosphate intermediate 2-methyllinalyl diphosphate to enable subsequent cyclization chemistry. MIBS does not exhibit catalytic activity with 2-fluorogeranyl diphosphate, and we recently reported the crystal structure of MIBS complexed with this unreactive substrate analogue [ Köksal, M., Chou, W. K. W., Cane, D. E., Christianson, D. W. (2012) Biochemistry 51 , 3011-3020 ]. However, cocrystallization of MIBS with the fluorinated analogue of the tertiary allylic diphosphate intermediate, 2-fluorolinalyl diphosphate, reveals unexpected reactivity for the intermediate analogue and yields the crystal structure of the complex with the primary allylic diphosphate, 2-fluoroneryl diphosphate. Comparison with the structure of the unliganded enzyme reveals that the crystalline enzyme active site remains partially open, presumably due to the binding of only two Mg(2+) ions. Assays in solution indicate that MIBS catalyzes the generation of (1R)-(+)-camphor from the substrate 2-fluorolinalyl diphosphate, suggesting that both 2-fluorolinalyl diphosphate and 2-methyllinalyl diphosphate follow the identical cyclization mechanism leading to 2-substituted isoborneol products; however, the initially generated 2-fluoroisoborneol cyclization product is unstable and undergoes elimination of hydrogen fluoride to yield (1R)-(+)-camphor.

PubMed: 23844678
DOI: 10.1021/bi400797c

Experimental method

X-RAY DIFFRACTION (1.849 Å)