Contribution of protein phosphorylation to binding-induced folding of the SLBP–histone mRNA complex probed by phosphorus-31 NMR

• SLBP is an intrinsically disordered protein (IDP) in the absence of RNA.
• A phosphothreonine in the SLBP RNA-binding domain stabilizes the SLBP–histone mRNA complex.
• This phosphate exhibits torsional strain as revealed by its 31P NMR chemical shift.
• Phosphates can play structural roles in stabilizing tertiary structure in IDPs.
• 31P NMR can be a good spectroscopic probe for folding of phosphorylated IDPs.

Phosphorus-31 (31P) NMR can be used to characterize the structure and dynamics of phosphorylated proteins. Here, I use 31P NMR to report on the chemical nature of a phosphothreonine that lies in the RNA binding domain of SLBP (stem-loop binding protein). SLBP is an intrinsically disordered protein and phosphorylation at this threonine promotes the assembly of the SLBP–RNA complex. The data show that the 31P chemical shift can be a good spectroscopic probe for phosphate-coupled folding and binding processes in intrinsically disordered proteins, particularly where the phosphate exhibits torsional strain and is involved in a network of hydrogen-bonding interactions.

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