CO-Sensing Mechanisms

Abstract

Carbon monoxide (CO) has long been known to have dramatic physiological effects on organisms ranging from bacteria to humans, but recently there have a number of suggestions that organisms might have specific sensors for CO. This article reviews the current evidence for a variety of proteins with demonstrated or potential CO-sensing ability. Particular emphasis is placed on the molecular description of CooA, a heme-containing CO sensor from Rhodospirillum rubrum, since its biological role as a CO sensor is clear and we have substantial insight into the basis of its sensing ability

Transcriptional Activation of Dehalorespiration

“…For proteins like CprK in the CRP/ FNR family, binding of the ligand to the effector domain triggers interactions of the helix-turn-helix DNA-binding domain with a specific upstream regulatory DNA sequence. The conformational changes responsible for ligand-induced DNA binding have been reviewed and appear to involve a hinge region between the two domains and the repositioning of a long helix at the dimer interface (18,19).…”

CO metabolism, sensing, and signaling

“…CooA acts also as a redox sensor [61]; indeed, CO is able to bind only the reduced form of CooA, this causing a protein conformational change(s) necessary for DNA binding and thereby for CooA-dependent gene transcription [60]. Recent studies suggest that changes in the heme ligation alter the structure stability of the heme domain and of the dimer interface, without altering the stability of the DNAbinding domain [66].…”

“…The best known CO-sensors is CooA, a homodimeric heme-containing protein, which regulates the CO oxidation system in the photosynthetic bacterium Rodospirillum rubrum [59][60][61][62], and the mammalian neuronal (N) period circadian protein (Per)-aryl hydrocarbon receptor nuclear translocator protein (Arnt) -single-minded protein (Sim) protein 2 (NPAS2), a member of the bHLH family of transcription factors expressed in the forebrain, which is a CO-dependent regulator of the circadian rhythm [59,60,63].…”

Chelatases: distort to select?

“…The resulting metalated tetrapyrroles constitute the centerpiece for proteins involved in cellular processes ranging from oxygen and electron transport, signal transduction, photosynthesis, and sulfur and nitrogen metabolism to molecular rearrangements, methyl-group transfer reactions and regulation of transcription and translation [1][2][3][4]. Metalated tetrapyrroles such as the cofactors and prosthetic groups heme, chlorophyll, cobalamin (vitamin B 12 ) and coenzyme F 430 have a centrally chelated metal ion and arise from a common tetrapyrrole, uroporphyrinogen III.…”