Article links to this publication which has all the information needed:
It is mentioned in the paper that:
Although we found only 4% variability in genomic nucleotides between
SARS-CoV-2 and a bat SARS-related coronavirus (SARSr-CoV; RaTG13), the
difference at neutral sites ...
Without seeing the sequence of the RNA-binding protein it is impossible to be sure, but the obvious conclusion is:
The RNA-binding protein is a peptidyl-prolyl cis-trans isomerase.
It has been known since 1989 that peptidyl-prolyl cis-trans isomerase is a multiple-function protein, also exhibiting properties of the cyclophilins, proteins which bind ...