Fe/S proteins in microbial sulfur oxidation

Area of Science:

• Biochemistry
• Microbiology
• Evolutionary Biology

Background:

• Iron-sulfur (Fe/S) clusters are essential cofactors in all domains of life.
• Fe/S proteins play critical roles in microbial sulfur metabolism, particularly in dissimilatory sulfur oxidation.
• Two key pathways, rDsr and sHdr, are involved in oxidizing sulfane sulfur to sulfite.

Purpose of the Study:

• To investigate the Fe/S cluster machineries required for the rDsr and sHdr pathways.
• To understand the novel pathway involving Radical SAM proteins (LipS1 and LipS2) in the sHdr pathway.
• To map the Fe/S cluster biogenesis systems (ISC, SUF, MIS, SMS) supporting these sulfur oxidation pathways.

Main Methods:

• Bioinformatic analysis of Fe/S cluster machineries across sulfur-oxidizing prokaryotes.
• Characterization of the sHdr pathway's dependence on lipoate-binding proteins and Radical SAM enzymes.
• Investigating the coordination patterns of auxiliary Fe/S clusters by LipS1 and LipS2.

Main Results:

• ISC, SUF, MIS, and SMS Fe/S cluster systems are sufficient for rDsr and sHdr pathway operation.
• The sHdr pathway relies on a novel assembly pathway involving two Radical SAM proteins, LipS1 and LipS2.
• LipS1 and LipS2 coordinate unique Fe/S clusters and function as lipoyl synthases, inserting sulfur into an octanoyl residue.

Conclusions:

• The study elucidates the Fe/S cluster requirements and novel biogenesis mechanisms for key microbial sulfur oxidation pathways.
• Understanding these pathways provides insights into ancient biogeochemical cycles and microbial metabolism.
• The findings highlight the diversity and adaptability of Fe/S protein function in biological systems.