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A New Tessera into the Interactome of the isc Operon: A Novel Interaction between HscB and IscS

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ABSTRACT

Iron sulfur clusters are essential universal prosthetic groups which can be formed inorganically but, in biology, are bound to proteins and produced enzymatically. Most of the components of the machine that produces the clusters are conserved throughout evolution. In bacteria, they are encoded in the isc operon. Previous reports provide information on the role of specific components but a clear picture of how the whole machine works is still missing. We have carried out a study of the effects of the co-chaperone HscB from the model system E. coli. We document a previously undetected weak interaction between the chaperone HscB and the desulfurase IscS, one of the two main players of the machine. The binding site involves a region of HscB in the longer stem of the approximately L-shaped molecule, whereas the interacting surface of IscS overlaps with the surface previously involved in binding other proteins, such as ferredoxin and frataxin. Our findings provide an entirely new perspective to our comprehension of the role of HscB and propose this protein as a component of the IscS complex.

No MeSH data available.


Scheme to illustrate the possible regulation of the IscS interactions. Different effectors may signal which components are bound to IscS at any time point keeping in mind that IscS is a dimer. The possibility of occupying two independent binding sites also makes room for the possibility that allosteric mechanisms may operate.
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Figure 7: Scheme to illustrate the possible regulation of the IscS interactions. Different effectors may signal which components are bound to IscS at any time point keeping in mind that IscS is a dimer. The possibility of occupying two independent binding sites also makes room for the possibility that allosteric mechanisms may operate.

Mentions: Another aspect that our research reveals is how the multiple interactions of IscS with very different proteins involve the same surface of interaction. This will require a tight regulation on which specific protein is bound at the different time points. A possible way to explain our findings is to remember that IscS is a dimer (Figure 7). This means that, in the presence of different suitable effectors, different interactions may in principle be possible on the two IscS protomers leading to a complex but efficient regulation according to an allosteric mechanism.


A New Tessera into the Interactome of the isc Operon: A Novel Interaction between HscB and IscS
Scheme to illustrate the possible regulation of the IscS interactions. Different effectors may signal which components are bound to IscS at any time point keeping in mind that IscS is a dimer. The possibility of occupying two independent binding sites also makes room for the possibility that allosteric mechanisms may operate.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037179&req=5

Figure 7: Scheme to illustrate the possible regulation of the IscS interactions. Different effectors may signal which components are bound to IscS at any time point keeping in mind that IscS is a dimer. The possibility of occupying two independent binding sites also makes room for the possibility that allosteric mechanisms may operate.
Mentions: Another aspect that our research reveals is how the multiple interactions of IscS with very different proteins involve the same surface of interaction. This will require a tight regulation on which specific protein is bound at the different time points. A possible way to explain our findings is to remember that IscS is a dimer (Figure 7). This means that, in the presence of different suitable effectors, different interactions may in principle be possible on the two IscS protomers leading to a complex but efficient regulation according to an allosteric mechanism.

View Article: PubMed Central - PubMed

ABSTRACT

Iron sulfur clusters are essential universal prosthetic groups which can be formed inorganically but, in biology, are bound to proteins and produced enzymatically. Most of the components of the machine that produces the clusters are conserved throughout evolution. In bacteria, they are encoded in the isc operon. Previous reports provide information on the role of specific components but a clear picture of how the whole machine works is still missing. We have carried out a study of the effects of the co-chaperone HscB from the model system E. coli. We document a previously undetected weak interaction between the chaperone HscB and the desulfurase IscS, one of the two main players of the machine. The binding site involves a region of HscB in the longer stem of the approximately L-shaped molecule, whereas the interacting surface of IscS overlaps with the surface previously involved in binding other proteins, such as ferredoxin and frataxin. Our findings provide an entirely new perspective to our comprehension of the role of HscB and propose this protein as a component of the IscS complex.

No MeSH data available.