Insight on flavinylation and functioning factor in Type B succinate dehydrogenase from Gram-positive bacteria

Area of Science:

• Biochemistry
• Molecular Biology
• Microbiology

Background:

• Succinate dehydrogenase (SDH) is a crucial enzyme complex catalyzing succinate oxidation and quinone reduction.
• Understanding SDH maturation is vital, especially in Gram-positive bacteria where mechanisms remain unclear.

Purpose of the Study:

• To investigate the maturation process of Type B SDH in Gram-positive bacteria.
• To elucidate the roles of subunits and cofactors in SDH assembly and function.

Main Methods:

• Heterologous expression of three SDH enzymes from distinct Gram-positive bacteria in Escherichia coli.
• Analysis of flavinylation and iron-sulfur cluster incorporation in expressed SDH subunits.

Main Results:

• Covalent flavin adenine dinucleotide (FAD) binding to SDH flavoprotein subunits occurred in a complex with the iron-sulfur subunit.
• Flavinylation was enhanced by the presence of the iron-sulfur subunit and fumarate.
• Iron-sulfur subunits lacking SDH activity did not incorporate iron-sulfur clusters, indicating separate maturation requirements.

Conclusions:

• SDH flavinylation is dependent on the assembly of a complex involving the flavoprotein and iron-sulfur subunits.
• Iron-sulfur cluster maturation requires additional factors not solely dependent on flavinylation or complex formation.