title: The rubrerythrin-like protein Hsp21 of Clostridium acetobutylicum is a general stress protein.
abstract: The small heat shock protein Hsp21 of Clostridium acetobutylicum was recently identified as a rubrerythrin-like protein with a rubredoxin-like FeS(4) domain at the N-terminus and a ferritin-like diiron domain at the C-terminus. Here, we report that the two identical tandem genes rbr3A and rbr3B, which encode the heat shock protein Hsp21, show the transcription pattern of general stress genes. Northern blot analysis indicated that the transcription of the rbr3AB operon is induced by various environmental stress conditions: in addition to heat and oxidative stress, an increase of the pH of the growth medium from 4.5 to 6.2, addition of the salt NaCl (400 mM) or of the solvent butanol (3.5% v/v), and lowering the incubation temperature from 37 to 25 degrees C resulted in transiently increased transcript levels. The promoter region deduced from the 5' end of the mRNA has only limited similarity to the consensus promoter sequence of Gram-positive bacteria. A conserved inverted repeat between this promoter and the initiation codon is proposed to have a regulatory role. Although C. acetobutylicum is regarded as a strictly anaerobic bacterium, live/dead staining demonstrated that it can survive exposure to air or H(2)O(2) and other stressors to various extents.
authors.affiliation: Division of Microbiology, Institute of Biological Sciences, University of Rostock, Albert-Einstein-Str. 3, 18051, Rostock, Germany.
authors.forename: Falk
authors.initials: F
authors.lastname: Hillmann
authors.forename: Ralf-Jörg
authors.initials: RJ
authors.lastname: Fischer
authors.forename: Hubert
authors.initials: H
authors.lastname: Bahl
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003015:Clostridium Infections / Q000378:metabolism; D046969:Clostridium acetobutylicum / Q000235:genetics* / Q000378:metabolism; D005288:Ferredoxins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006422:Hemerythrin; D008969:Molecular Sequence Data; D009876:Operon; D012333:RNA, Messenger / Q000378:metabolism; D012416:Rubredoxins / Q000737:chemistry; D024363:Transcription Initiation Site
chemical_list: D001426:Bacterial Proteins; D005288:Ferredoxins; D006360:Heat-Shock Proteins; D006422:Hemerythrin; D012333:RNA, Messenger; D012416:Rubredoxins; C055857:rubrerythrins