NMR structure and functional studies of two proteins from methanobacterium thermoautrophicum

This project was under taken as part of the 'Structural Proteomics Initiative' from the Ontario Cancer Institute. The structures of two proteins (MTH0807 and MTH0776) from Methanobacterium thermoautotrophicum (strain DeltaH) was determined by NMR spectroscopy to aid the prediction of their function. Using structure analysis and visualization tools in addition to modern NMR spectroscopy and comparative biochemical assays, we have shown (in chapter 2) that it may be possible to engineer multiple functions (thioredoxin and glutaredoxin activities) into MTH0807. This will be particularly useful in the technological application of MTH0807 as it is very stable and seems to withstand the deleterious effects that most proteins could not tolerate. In chapter 3, our analysis also indicated that MTH0807 is indeed a true thioredoxin, contrary to earlier suggestions by previous workers that MTH0807 may be part of a distinct ribonucleotide-reducing system involving ferredoxins and ferredoxin-thioredoxin reductases. In chapter 4 of this thesis, the three dimensional structure of MTH0776, a 101 amino acid residue protein specific to the methanogenic archaebacteria with no known function or structure was determined. It exhibited a novel fold hence no known function could be predicted from its structure. Our extensive comparative genomic analysis however shows that MTH0776 is part of a two-protein operon with its upstream partner---MTH0777, which is also specific to methanogenic archaebacteria. The fact that this two-component operon is conserved in all methane metabolizing archaea, strongly suggests that both proteins have an important role in methanogenesis. Analysis shows that MTH0776 and MTH0777 bind together and may be part of a transport system conserved in the methanogenic archaebacteria.