Sohlberg, et al. present characterization of two proteins from Streptomyces coelicolor. The protein in this family was shown to have poly(A) polymerase activity and may be responsible for polyadenylating RNA in this species. Reference 2 showed that a nearly identical plasmid-encoded protein from Streptomyces antibioticus is a bifunctional enzyme that acts also as a guanosine pentaphosphate synthetase.
Jiyao W et al.(2023). "The conserved domain database in 2023.",