Structure of a Virulence Regulatory Factor CvfB Reveals a Novel Winged Helix RNA Binding Module

SummaryCvfB is a conserved regulatory protein important for the virulence of Staphylococcus aureus. We show here that CvfB binds RNA. The crystal structure of the CvfB ortholog from Streptococcus pneumoniae at 1.4 Å resolution reveals a unique RNA binding protein that is formed from a concatenation of well-known structural modules that bind nucleic acids: three consecutive S1 RNA binding domains and a winged helix (WH) domain. The third S1 and the WH domains are required for cooperative RNA binding and form a continuous surface that likely contributes to the RNA interaction. The WH domain is critical to CvfB function and contains a unique sequence motif. Thus CvfB represents a novel assembly of modules for binding RNA.

► CvfB is an RNA binding protein involved in bacterial virulence
► CvfB consists of three consecutive S1 domains and a C-terminal winged helix (WH) domain
► The WH domain and the third S1 domain are involved in cooperative binding of RNA
► WH contains a novel nucleic acid recognition motif