title: HMG-CoA reductase is regulated by salinity at the level of transcription in Haloferax volcanii.
abstract: The moderately halophilic archaeon Haloferax volcanii was surveyed for protein profile changes correlated with growth at high and low salinity. A single polypeptide with an approximate mass of 46 kDa was conspicuously more abundant during growth at high salinity. This protein was identified as HMG-CoA reductase (HMGR), encoded by the hmgR gene. HMGR is a key enzyme in the mevalonate pathway of isoprenoid biosynthesis, the sole route in haloarchaea for lipid and carotenoid production. Enzymatic assays confirmed that HMGR activity is more abundant in cells grown at high salinity. Low salt cultures of H. volcanii contained lower amounts of hmgR transcript compared to cells grown in high salt suggesting that the observed regulation occurs at the level of transcription. Paradoxically, both lipid and carotenoid content decreased in H. volcanii grown at high salinity despite the increased levels of HMGR specific activity. To our knowledge, this is the first report demonstrating that the expression of HMGR is regulated in response to non-optimal salinity in a halophilic archaeon.
authors.affiliation: Department of Biology, Rider University, Lawrenceville, NJ 08648, USA. kbidle@rider.edu
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Bidle
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Hanson
authors.forename: Koko
authors.initials: K
authors.lastname: Howell
authors.forename: Jennifer
authors.initials: J
authors.lastname: Nannen
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D019848:Gene Expression Regulation, Archaeal; D015971:Gene Expression Regulation, Enzymologic; D019622:Haloferax volcanii / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012965:Sodium Chloride / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D019843:Archaeal Proteins; D012333:RNA, Messenger; D002338:Carotenoids; D012965:Sodium Chloride; D006903:Hydroxymethylglutaryl CoA Reductases