A single sensor controls large variations in zinc quotas in a marine cyanobacterium

Abstract

Marine cyanobacteria are critical players in global nutrient cycles that crucially depend on trace metals in metalloenzymes, including zinc for CO2 fixation and phosphorus acquisition. How strains proliferating in the vast oligotrophic ocean gyres thrive at ultra-low zinc concentrations is currently unknown. Using Synechococcus sp. WH8102 as a model we show that its zinc-sensor protein Zur differs from all other known bacterial Zur proteins in overall structure and the location of its sensory zinc site. Uniquely, Synechococcus Zur activates metallothionein gene expression, which supports cellular zinc quotas spanning two orders of magnitude. Thus, a single zinc sensor facilitates growth across pico- to micromolar zinc concentrations with the bonus of banking this precious resource. The resultant ability to grow well at both ultra-low and excess zinc, together with overall lower zinc requirements, likely contribute to the broad ecological distribution of Synechococcus across the global oceans.

Characterization of the Zinc Uptake Repressor (Zur) from Acinetobacter baumannii

“…How transition metal binding by FUR family proteins allosterically activate the homodimer for high affinity DNA binding and transcription repression or target gene expression is a subject of long-standing interest in the metallosensor field, 17 made even more interesting by recent work that establishes that Zn-Zur can function as an activator of transcription. 30,32 Early crystallographic studies suggested that FUR proteins, e.g., Bacillus subtilis PerR undergo a large "open-to-closed" conformation transition in which the open state have been described as nearly linear, 65,66 while more recent crystallographic studies of X. campestris Zur reveal a conformational "switch" that involves a "closed-to-open" conformational change from a tightly packed V-shaped structure to a more open structure that resembles, but is not identical to, the structure of the DNA-bound Zn-Zur complex (see Figure 1A). 31 This conformational change involves a dramatic ≈130°rotation of one subunit relative to the other, where the DNA binding domain pivots around hinge point, very near the regulatory Cys (C110 in XcZur).…”

“…Zur proteins are typically homodimeric (some FUR proteins are tetrameric), where each subunit is composed of two domains, a C-terminal dimerization domain and an N-terminal DNA binding domain. , The C-terminal domain harbors a structural tetrathiolate (S 4 ) zinc site (denoted site 1) that maintains the structural integrity of the dimer, and one or two regulatory or allosteric metal sites depending upon the organism. At least one of these allosteric sites is common to all Zur proteins, is generally found at the interfacial region or hinge between the two domains, and is nearly always coordinated by one Cys and three nonthiolate ligands (site 2). ,− Some Zur proteins harbor a third metal site (site 3) that is also regulatory but binds Zn II slightly more weakly, thus, allowing for what has been termed a “graded” zinc deficiency response. Here, various classes of Zur-regulated genes become derepressed at distinct degrees or “waves” of cellular zinc depletion, , which may also be true for other FUR family regulators, including Fe-regulated Fur. , …”

“…Although Zur is generally regarded as a zinc-activated repressor, recent work reveals that Zn II -bound Zur also functions as a transcriptional activator at some promoters, including those that encode transporters that mediate zinc efflux or intracellular chelators that mediate zinc sequestration. ,, Recent structural studies reveal that activation requires cooperative polymerization of Zn-Zur dimers on the promoter upstream of the −35 element of the promoter and involves a direct interaction with the C-terminal domain of the α-subunit of RNA polymerase . In contrast, Zn-Zur bound to a repressing site typically accommodates one or two dimers depending on the operator-promoter sequence; the structure of Escherichia coli Zur reveals a 2:1 dimer:DNA complex, with Zur dimers bound on opposite sides of the DNA .…”

Exploring the key factors affecting the seasonal variation of phytoplankton in the coastal Yellow Sea

“…For instance, Zn is an essential element in key phytoplankton biochemical functions within an optimal concentration range. Recent studies have also suggested that Zn may be involved in the biological function and adaptive evolution of phytoplankton (Mikhaylina et al, 2022;Ye et al, 2022). In contrast, Hg is thought to be a hazardous metal that can be accumulated by phytoplankton as well as zooplankton, but zooplankton are much more sensitive to Hg than phytoplankton (Zhu et al, 2020;Abdou and Tercier-Waeber, 2022).…”

Ultra‐Stretchable, Adhesive, and Anti‐Swelling Ionogel Based on Fluorine‐Rich Ionic Liquid for Underwater Reliable Sensor

“…[12] Ionic-liquid-based gels (ionogel) have received a lot of interest in soft materials and applied widely in soft robotics, humanmachine interfaces and healthcare. [2,9,13,14] Particularly, the hydrophobic ionic liquids have revealed great potential in ionogels for wearable device and underwater sensing application.…”