A systematic approach to the amplified expression, functional characterization and purification of inositol transporters from Bacillus subtilis.
Abstract   A systematic approach was used for the cloning and amplified expression in Escherichia coli of the genes for each of three inositol transport proteins (IolF, IolT, YfiG) from Bacillus subtilis that are evolutionarily-related to human transporters. Inducible amplified expression of each was achieved to levels of ∼ 10-15% of total protein in E. coli inner membrane preparations. The functional integrity of each heterologously-expressed protein was demonstrated by measuring the kinetics of (3)H-myo-inositol transport into energized whole cells; this confirmed that IolT is the major inositol transporter, IolF is an inefficient transporter of this substrate and demonstrated that YfiG is an inositol transport protein for the first time. Competition for (3)H-myo-inositol transport by 17 unlabelled compounds revealed all three proteins to be highly specific in recognizing inositols over sugars. IolT was confirmed to be highly specific for both myo- and D-chiro-inositol and IolF was confirmed to prefer D-chiro-inositol over myo-inositol. YfiG selectively recognized myo-inositol, D-chiro-inositol and, uniquely, L-chiro-inositol. All three proteins were successfully solubilized and purified in milligram quantities from inner membrane preparations and their suitability for inclusion in crystallization trials was assessed by analysis of structural integrity and thermal stability using circular dichroism spectroscopy followed by examination for monodispersity using gel filtration chromatography.
Astbury Centre for Structural Molecular Biology, University of Leeds, UK.
Kim E
KE
Bettaney
Preethi
P
Sukumar
Rohanah
R
Hussain
Giuliano
G
Siligardi
Peter J F
PJ
Henderson
Simon G
SG
Patching
D001412:Bacillus subtilis / Q000235:genetics*; D001692:Biological Transport; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D007294:Inositol / Q000737:chemistry / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; D007294:Inositol