The Mycobacterium tuberculosis protein Rv2302 has been characterized using nuclear magnetic resonance （NMR） and circular dichroism （CD） spectroscopy. While the biochemical function of Rv2302 is still unknown, rece...The Mycobacterium tuberculosis protein Rv2302 has been characterized using nuclear magnetic resonance （NMR） and circular dichroism （CD） spectroscopy. While the biochemical function of Rv2302 is still unknown, recent microarray analyses show that Rv2302 is upregulated in response to starvation and overexpression of heat shock proteins and, consequently, may play a role in the biochemical processes associated with these events. Rv2302 is a monomer in solution as shown by size exclusion chromatography and NMR spectroscopy. CD spectroscopy suggests that Rv2302 partially unfolds upon heating and that this unfolding is reversible. Using NMR-based methods, the solution structure of Rv2302 was determined. The protein contains a five-strand, antiparalle β-sheet core with one C-terminal α-helix （A61 to A75） nestled against its side. Hydrophobic interactions between residues in the α-helix and β-strands 3 and 4 hold the α-helix near the β-sheet core. The electrostatic potential on the solvent-accessible surface is primarily negative with the exception of a positive arginine pocket composed of residues R18, R70, and R74. Steady-state {^1H}-^15N heteronuclear nuclear Overhauser effects indicate that the protein＇s core is rigid on the picosecond timescale. The absence of amide cross-peaks for residues G 13 to H 19 in the ^1H-^15N heteronuclear single quantum correlation spectrum suggests that this region, a loop between β-strands 1 and 2, undergoes motion on the millisecond to microsecond timescale. Dali searches using the structure closest to the average structure do not identify any high similarities to any other known protein structure, suggesting that the structure of Rv2302 may represent a novel protein fold.展开更多
文摘The Mycobacterium tuberculosis protein Rv2302 has been characterized using nuclear magnetic resonance （NMR） and circular dichroism （CD） spectroscopy. While the biochemical function of Rv2302 is still unknown, recent microarray analyses show that Rv2302 is upregulated in response to starvation and overexpression of heat shock proteins and, consequently, may play a role in the biochemical processes associated with these events. Rv2302 is a monomer in solution as shown by size exclusion chromatography and NMR spectroscopy. CD spectroscopy suggests that Rv2302 partially unfolds upon heating and that this unfolding is reversible. Using NMR-based methods, the solution structure of Rv2302 was determined. The protein contains a five-strand, antiparalle β-sheet core with one C-terminal α-helix （A61 to A75） nestled against its side. Hydrophobic interactions between residues in the α-helix and β-strands 3 and 4 hold the α-helix near the β-sheet core. The electrostatic potential on the solvent-accessible surface is primarily negative with the exception of a positive arginine pocket composed of residues R18, R70, and R74. Steady-state {^1H}-^15N heteronuclear nuclear Overhauser effects indicate that the protein＇s core is rigid on the picosecond timescale. The absence of amide cross-peaks for residues G 13 to H 19 in the ^1H-^15N heteronuclear single quantum correlation spectrum suggests that this region, a loop between β-strands 1 and 2, undergoes motion on the millisecond to microsecond timescale. Dali searches using the structure closest to the average structure do not identify any high similarities to any other known protein structure, suggesting that the structure of Rv2302 may represent a novel protein fold.
