Multi-heme cytochromes--new structures, new chemistry

Area of Science:

• Biochemistry
• Microbiology
• Structural Biology

Background:

• Heme is a vital cofactor, with c-type cytochromes being a major protein family.
• Bacterial genomics reveals numerous novel c-type cytochromes with multiple heme groups.
• Geobacter sulfurreducens possesses abundant multi-heme cytochromes, impacting its respiratory capabilities.

Purpose of the Study:

• To review recent advances in structural and functional analyses of multi-heme cytochromes.
• To highlight the significance of these proteins in bacterial respiration and novel chemistries.
• To focus on specific catalytic activities and structural features.

Main Methods:

• Genomic analysis to identify novel c-type cytochromes.
• Structural analysis of multi-heme proteins.
• Functional studies of enzymatic activities, including nitrite reductase, hydroxylamine oxidoreductase, and tetrathionate reductase.

Main Results:

• Identification of a large number of multi-heme cytochromes in Geobacter sulfurreducens.
• Discovery of associated enzymatic activities in many multi-heme cytochromes, revealing new biochemical pathways.
• Characterization of specific multi-heme cytochromes from Geobacter and Desulfovibrio species.

Conclusions:

• Multi-heme cytochromes are essential for bacterial respiratory flexibility and metabolic diversity.
• Structural modules in these cytochromes show repeating patterns, aiding in their functional understanding.
• Ongoing research continues to unveil new enzymatic functions and structural insights into these critical proteins.