Evolution avoids a pathological stabilizing interaction in the immune protein S100A9

• Published in: bioRxiv
• Main Authors: Harman, Joseph L, Reardon, Patrick N, Costello, Shawn M, Warren, Gus D, Phillips, Sophia R, Connor, Patrick J, Marqusee, Susan, Harms, Michael J
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 09.05.2022
• Subjects: Amino acids; Evolution; Mutation; Proteins; S100A9 protein
• DOI: 10.1101/2022.05.09.490804

Protein stability constrains protein evolution. While much is known about evolutionary constraints on destabilizing mutations, much less is known about evolutionary constraints on mutations that increase protein stability. We recently found that the M63F mutation in the innate immune protein S100A9 increases its stability but disrupts its natural ability to activate inflammation. Here we show, through careful biophysical and functional studies, that this mutation stabilizes a nonfunctional form of the protein through a direct interaction with another amino acid, Phe37. Phe can be tolerated at position 37 or 63, but not at both sites simultaneously. We find that this pattern has been conserved over millions of years of evolution. Our work highlights an underappreciated evolutionary constraint on stabilizing mutations: they must avoid inappropriately stabilizing non-functional protein conformations. Competing Interest Statement The authors have declared no competing interest. Footnotes * https://github.com/harmslab/stability-constraint-ms-figures