SPECIFIC INVITRO GUANYLYLATION OF A 43-KILODALTON MEMBRANE-ASSOCIATEDPROTEIN OF STREPTOMYCES-COELICOLOR

Incubation of [alpha-P-32]GTP with cellular extracts or membranes of S treptomyces coelicolor labels a protein of 43 kDa, which was also labe led with [8,5'-H-3]GTP but not with [alpha-P-32]ATP or [gamma-P-32]GTP . Radioactivity remained associated with this protein after boiling in 0.1 N NaOH, but it was dissociated after incubation in 0.1 N HCl or h ydroxylamine. Chromatographic analysis of the HCl-dissociated compound showed that GMP was the covalently bound nucleotide. Furthermore, gua nylylation appeared to be reversible and to take place by a pyrophosph orylytic mechanism. Guanylylation was more efficient at low temperatur es. Several Streptomyces species showed a guanylylated protein with a similar molecular mass.