Extracellular low-molecular weight guanyl-preferring
ribonucleases (LMW RNases) of Bacillus sp. comprise a group of hydrolytic
enzymes that share highly similar structural and catalytic characteristics with
barnase, a
ribonuclease from Bacillus amyloliquefaciens, and
binase, a
ribonuclease from Bacillus intermedius. Although the physical-chemical and catalytic properties of Bacillus guanyl-preferring
ribonucleases are very similar, there is considerably more variation in the environmental conditions that lead to the induction of the genes encoding these RNases. Based on structural differences of their genes the guanyl-preferring
ribonucleases have been sub-divided into
binase-like and
barnase-like groups. Here we show the ability of the key regulator of
phosphate deficiency response, PhoP, to direct the transcription of the
binase-like RNases but not
barnase-like RNases. These results, together with our demonstration that
binase-like RNases are induced in response to
phosphate starvation, allow us to categorise this group of
ribonucleases as new members of Bacillus PhoP regulon. In contrast, the
barnase-like
ribonucleases are relatively insensitive to the
phosphate concentration and the environmental conditions that are responsible for their induction, and the regulatory elements involved, are currently unknown.