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Updated: Jun 16, 2026

A Pipeline to Investigate the Structures and Signaling Pathways of Sphingosine 1-Phosphate Receptors
Published on: June 8, 2022
The regulatory factor SipA is a highly stable beta-II class protein with a SH3 fold
María Luisa López-Redondo1, Asunción Contreras, Alberto Marina
1Macromolecular Crystallography Unit, Instituto de Biomedicina de Valencia (CSIC) and CIBERER, 46010 Valencia, Spain.
Abstract:
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.
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