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The regulatory factor SipA is a highly stable β‐II class protein with a SH3 fold
Author(s) -
López-Redondo María Luisa,
Contreras Asunción,
Marina Alberto,
Neira José L.
Publication year - 2010
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2010.01.043
Subject(s) - circular dichroism , histidine kinase , biophysics , chemistry , histidine , random coil , crystallography , biochemistry , biology , enzyme
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 1 H NMR spectroscopies, as well as modelling, suggest that SipA is a β‐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 (Δ C p ) closely agreed with the corresponding theoretical values predicted from the structural model, further supporting its accuracy.