The regulatory factor SipA is a highly stable beta-II class protein with a SH3 fold.
The small regulator SipA, interacts with the ATP-binding domain of non-bleaching sensor histidine kinase (NblS), the most conserved histidine kinase in cyanobacteria. NblS regulates photosynthesis and acclimation to a variety of environmental conditions. We show here that SipA is a highly stable protein in a wide pH range, with a thermal denaturation midpoint of 345 K. Circular dichroism and 1D 1H NMR spectroscopies, as well as modelling, suggest that SipA is a beta-II class protein, with short strands followed by turns and long random-coil polypeptide patches, matching the SH3 fold. The experimentally determined m-value and the heat capacity change upon thermal unfolding (DeltaCp) closely agreed with the corresponding theoretical values predicted from the structural model, further supporting its accuracy.
López-Redondo
María Luisa
ML
Macromolecular Crystallography Unit, Instituto de Biomedicina de Valencia (CSIC) and CIBERER, 46010 Valencia, Spain.
Contreras
Asunción
A
Marina
Alberto
A
Neira
José L
JL
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D017510:Protein Folding; D055550:Protein Stability; D013816:Thermodynamics; D018909:src Homology Domains / Q000502:physiology*
D001426:Bacterial Proteins