A novel secreted ribonuclease from Bacillus intermedius: gene structure and regulatory control

Abstract

A second secreted ribonuclease, designated binase II, has been detected in Bacillus intermedius 7P, and its structural gene was cloned and sequenced. Unlike the well-known binase I, a 109-amino acid guanyl-specific enzyme, the 292-residue binase II is closely related to the B. subtilis nuclease Bsn, in structure and in its enzymatic properties. Binase II is also insensitive to inactivation by barstar, an inhibitor protein that is specific for guanyl-specific ribonucleases. While both B. intermedius enzymes are induced upon phosphate starvation, only the gene for binase I belongs to the pho regulon system and carries pho-box elements adjacent to its promoter sequence. The gene for binase II is similar to that for Bsn in lacking such elements. The birB gene coding for binase II appears to be located next to the 3'-end of a ferric ion transport operon, with which it convergently overlaps. This would allow attenuator control over binase II expression under conditions of starvation for ferric ions.

New Insight into Secreted Ribonuclease Structure: Binase Is a Natural Dimer

“…Almost all known bacteria secrete extracellular RNases. Bacilli produce at least 2 types of RNases, the “high-molecular weight” RNases [32] and small guanyl-specific RNases, among which binase, the thermostable enzyme from B. pumilus (originally named B. intermedius ), and barnase from B. amyloliquefaciens are the best characterised [4] , [11] , [25] , [27] . Despite classical reports describing the monomeric form of binase [11] , [27] , many studies have demonstrated the dimerisation of binase in crystals [8] , [13] , [14] , [33] .…”

Mechanisms of Plant Tolerance to RNA Viruses Induced by Plant-Growth-Promoting Microorganisms

“…Among endophytic microorganisms isolated from diverse cultivated Cucurbitaceae, 73% of Bacillus, 27% of Paenibacillus, and 30% of Enterobacteriaceae isolates, as well as all Cronobacter, Pantoea, Microbacterium, and Staphylococcus isolates displayed RNase activity [65]. Interestingly, the secreted RNase (Bsn, 241 amino acids) from B. subtilis encoded by the bsn gene [66] is closely related in structure and in its enzymatic properties to the B. pumilus nuclease binase II (292 amino acids) encoded by the birB gene [67].…”

Barnase and binase: twins with distinct fates

“…Lethal expression of the gene for barnase alone without barstar in B. subtilis host cells [23] supports this assumption. The YrdF protein is likely to inhibit another type of secreted RNase in Bacillus , namely high‐molecular‐weight RNase Bsn or binase II [35,36]. These nonspecific RNases cleave RNA molecules with the formation of 5′‐terminal phosphate products, compared with the hydrolysis of RNA to produce ribonucleotide‐3′‐phosphates by guanyl‐preferring RNAses.…”