Limits...
Intracellular iron sensing by the direct binding of iron to regulators.

Kobayashi T, Nishizawa NK - Front Plant Sci (2015)

View Article: PubMed Central - PubMed

Affiliation: Japan Science and Technology Agency, PRESTO Kawaguchi, Japan ; Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University Nonoichi, Japan.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Iron (Fe) is an essential micronutrient for virtually all living organisms; it is incorporated into numerous proteins as Fe-sulfur (S) clusters, heme, or free Fe, and it mediates many metabolic processes, including photosynthesis and cellular respiration... Due to the low solubility and high reactivity of Fe, living cells must tightly regulate Fe acquisition in response to changes in Fe availability in the environment... The molecular components involved in Fe acquisition and its regulation have been studied extensively in plants, animals, fungi, and bacteria, revealing specific mechanisms in each kingdom... Fe acquisition in higher plants is mediated by a chelation-based pathway using mugineic acid family phytosiderophores (Strategy II) or a reduction-based pathway using ferric-chelate reductases (Strategy I), depending on the species (Römheld and Marschner, )... Fur from Escherichia coli is a transcriptional repressor that binds to cis-acting elements and ferrous Fe... When cellular Fe is scarce, Fur does not bind to Fe; this decreases the affinity between Fur and its cis-acting elements, releasing the repression of Fe uptake-related genes... Despite the diverse molecular mechanisms for Fe acquisition and regulation across kingdoms, all of the above-mentioned regulatory events are mediated by the direct binding of Fe or Fe-containing prosthetic groups (Fe-S clusters and heme) to regulatory proteins... Such direct Fe sensing is thought to be advantageous in rapidity and accuracy compared with indirect Fe sensing through metabolic changes, though the latter would also be important for fine-tuning the response... They showed that BTS produced in vitro using a wheat germ extract system was less abundant when Fe was included in the translation reaction mixture... This effect was abolished by a point mutation at a putative Fe-binding residue in the hemerythrin domain, suggesting that Fe binding to the hemerythrin domain destabilizes and inhibits the function of BTS... When expressed in planta, deletion of the hemerythrin domains from BTS resulted in increased protein stability... Further characterization of the mechanisms underlying the degradation and function of HRZs/BTS in relation to the binding of Fe, Zn, oxygen, or Fe-S clusters is essential to identify whether these regulators are central Fe sensors that determine downstream responses to Fe deficiency... It is possible that primary Fe sensing in plant cells is established by unknown factors, while IDEF1 and HRZs/BTS modulate these events and mediate appropriate Fe deficiency responses.

No MeSH data available.


Possible Fe signals recognized by IDEF1 and HRZs/BTS. (A) Known or putative binding of Fe and related molecules to domains of IDEF1 and HRZs/BTS. Solid and broken lines indicate known and putative bindings, respectively. M2+, divalent metal ions such as Zn, copper and nickel. HN, histidine-asparagine repeat; P, proline-rich region; Hr, hemerythrin domains; ZnF, Zn finger domains; Ru, rubredoxin-type fold. (B) Deduced effects of intracellular Fe deficiency on concentrations of Fe and related molecules which may act as Fe signals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4356067&req=5

Figure 1: Possible Fe signals recognized by IDEF1 and HRZs/BTS. (A) Known or putative binding of Fe and related molecules to domains of IDEF1 and HRZs/BTS. Solid and broken lines indicate known and putative bindings, respectively. M2+, divalent metal ions such as Zn, copper and nickel. HN, histidine-asparagine repeat; P, proline-rich region; Hr, hemerythrin domains; ZnF, Zn finger domains; Ru, rubredoxin-type fold. (B) Deduced effects of intracellular Fe deficiency on concentrations of Fe and related molecules which may act as Fe signals.

Mentions: Two types of Fe-binding regulators for Fe deficiency responses are known in higher plants: IDEF1 and HRZs/BTS (Figure 1A). IDEF1 is a Gramineae-specific transcription factor that positively regulates various genes involved in Fe uptake and translocation (Kobayashi et al., 2007, 2009). Analyses using transgenic rice plants revealed that IDEF1 is especially important for the early response to Fe deficiency. Nevertheless, IDEF1 transcription is not induced in response to Fe deficiency, suggesting that IDEF1 regulates Fe deficiency responses by receiving a signal. IDEF1 possesses characteristic histidine-asparagine repeats and proline-rich regions that bind ferrous Fe and other divalent metals reversibly (Figure 1A; Kobayashi et al., 2012). These metal-binding regions are essential for overexpressed IDEF1 to enhance Fe deficiency responses at the early stages of Fe deficiency, although a direct relationship between metal binding and IDEF1 function has not been proven.


Intracellular iron sensing by the direct binding of iron to regulators.

Kobayashi T, Nishizawa NK - Front Plant Sci (2015)

Possible Fe signals recognized by IDEF1 and HRZs/BTS. (A) Known or putative binding of Fe and related molecules to domains of IDEF1 and HRZs/BTS. Solid and broken lines indicate known and putative bindings, respectively. M2+, divalent metal ions such as Zn, copper and nickel. HN, histidine-asparagine repeat; P, proline-rich region; Hr, hemerythrin domains; ZnF, Zn finger domains; Ru, rubredoxin-type fold. (B) Deduced effects of intracellular Fe deficiency on concentrations of Fe and related molecules which may act as Fe signals.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4356067&req=5

Figure 1: Possible Fe signals recognized by IDEF1 and HRZs/BTS. (A) Known or putative binding of Fe and related molecules to domains of IDEF1 and HRZs/BTS. Solid and broken lines indicate known and putative bindings, respectively. M2+, divalent metal ions such as Zn, copper and nickel. HN, histidine-asparagine repeat; P, proline-rich region; Hr, hemerythrin domains; ZnF, Zn finger domains; Ru, rubredoxin-type fold. (B) Deduced effects of intracellular Fe deficiency on concentrations of Fe and related molecules which may act as Fe signals.
Mentions: Two types of Fe-binding regulators for Fe deficiency responses are known in higher plants: IDEF1 and HRZs/BTS (Figure 1A). IDEF1 is a Gramineae-specific transcription factor that positively regulates various genes involved in Fe uptake and translocation (Kobayashi et al., 2007, 2009). Analyses using transgenic rice plants revealed that IDEF1 is especially important for the early response to Fe deficiency. Nevertheless, IDEF1 transcription is not induced in response to Fe deficiency, suggesting that IDEF1 regulates Fe deficiency responses by receiving a signal. IDEF1 possesses characteristic histidine-asparagine repeats and proline-rich regions that bind ferrous Fe and other divalent metals reversibly (Figure 1A; Kobayashi et al., 2012). These metal-binding regions are essential for overexpressed IDEF1 to enhance Fe deficiency responses at the early stages of Fe deficiency, although a direct relationship between metal binding and IDEF1 function has not been proven.

View Article: PubMed Central - PubMed

Affiliation: Japan Science and Technology Agency, PRESTO Kawaguchi, Japan ; Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University Nonoichi, Japan.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

Iron (Fe) is an essential micronutrient for virtually all living organisms; it is incorporated into numerous proteins as Fe-sulfur (S) clusters, heme, or free Fe, and it mediates many metabolic processes, including photosynthesis and cellular respiration... Due to the low solubility and high reactivity of Fe, living cells must tightly regulate Fe acquisition in response to changes in Fe availability in the environment... The molecular components involved in Fe acquisition and its regulation have been studied extensively in plants, animals, fungi, and bacteria, revealing specific mechanisms in each kingdom... Fe acquisition in higher plants is mediated by a chelation-based pathway using mugineic acid family phytosiderophores (Strategy II) or a reduction-based pathway using ferric-chelate reductases (Strategy I), depending on the species (Römheld and Marschner, )... Fur from Escherichia coli is a transcriptional repressor that binds to cis-acting elements and ferrous Fe... When cellular Fe is scarce, Fur does not bind to Fe; this decreases the affinity between Fur and its cis-acting elements, releasing the repression of Fe uptake-related genes... Despite the diverse molecular mechanisms for Fe acquisition and regulation across kingdoms, all of the above-mentioned regulatory events are mediated by the direct binding of Fe or Fe-containing prosthetic groups (Fe-S clusters and heme) to regulatory proteins... Such direct Fe sensing is thought to be advantageous in rapidity and accuracy compared with indirect Fe sensing through metabolic changes, though the latter would also be important for fine-tuning the response... They showed that BTS produced in vitro using a wheat germ extract system was less abundant when Fe was included in the translation reaction mixture... This effect was abolished by a point mutation at a putative Fe-binding residue in the hemerythrin domain, suggesting that Fe binding to the hemerythrin domain destabilizes and inhibits the function of BTS... When expressed in planta, deletion of the hemerythrin domains from BTS resulted in increased protein stability... Further characterization of the mechanisms underlying the degradation and function of HRZs/BTS in relation to the binding of Fe, Zn, oxygen, or Fe-S clusters is essential to identify whether these regulators are central Fe sensors that determine downstream responses to Fe deficiency... It is possible that primary Fe sensing in plant cells is established by unknown factors, while IDEF1 and HRZs/BTS modulate these events and mediate appropriate Fe deficiency responses.

No MeSH data available.