A tight tunable range for Ni(II) sensing and buffering in cells

• Published in: Nature chemical biology Vol. 13; no. 4; pp. 409 - 414
• Main Authors: Foster, Andrew W, Pernil, Rafael, Patterson, Carl J, Scott, Andrew J P, Pålsson, Lars-Olof, Pal, Robert, Cummins, Ian, Chivers, Peter T, Pohl, Ehmke, Robinson, Nigel J
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.04.2017; Nature Publishing Group
• Subjects: 631/337/572; 631/45/321; 631/45/49/1141; 631/535/1266; Biochemical Engineering; Biochemistry; Bioorganic Chemistry; Buffers; Cell Biology; Cells; Chemistry; Chemistry/Food Science; Cyanobacteria; Deoxyribonucleic acid; DNA; Metal concentrations; Metals; Models, Molecular; Nickel; Nickel - analysis; Nickel - chemistry; Nickel - metabolism; Repressor Proteins - chemistry; Repressor Proteins - genetics; Repressor Proteins - metabolism; Sensors; Sensory perception; Synechocystis; Synechocystis - metabolism
• ISSN: 1552-4450; 1552-4469
• DOI: 10.1038/nchembio.2310

The Ni( ii ) affinity of Ni( ii ) sensor InrS is attuned to buffered Ni( ii ) concentrations, explaining why these two parameters co-vary for different metals over many orders of magnitude. The metal affinities of metal-sensing transcriptional regulators co-vary with cellular metal concentrations over more than 12 orders of magnitude. To understand the cause of this relationship, we determined the structure of the Ni( II ) sensor InrS and then created cyanobacteria ( Synechocystis PCC 6803) in which transcription of genes encoding a Ni( II ) exporter and a Ni( II ) importer were controlled by InrS variants with weaker Ni( II ) affinities. Variant strains were sensitive to elevated nickel and contained more nickel, but the increase was small compared with the change in Ni( II ) affinity. All of the variant sensors retained the allosteric mechanism that inhibits DNA binding following metal binding, but a response to nickel in vivo was observed only when the sensitivity was set to respond in a relatively narrow (less than two orders of magnitude) range of nickel concentrations. Thus, the Ni( II ) affinity of InrS is attuned to cellular metal concentrations rather than the converse.