8QK0

Crystal structure of cytochrome domain 3 from PgcA

Summary for 8QK0

• Entry DOI: 10.2210/pdb8qk0/pdb
• Related: 8QJ6 8QJG
• Descriptor: Lipoprotein cytochrome c, HEME C, SODIUM ION, ... (5 entities in total)
• Functional Keywords: cytochrome, geobacter sulfurreducens, extracellular electron transfer, mineral reduction., electron transport
• Biological source: Geobacter sulfurreducens PCA
• Total number of polymer chains: 2
• Total formula weight: 22753.20

Authors

Nash, B.W.,Edwards, M.J.,Clarke, T.A. (deposition date: 2023-09-14, release date: 2024-11-06)

Primary citation

Nash, B.W.,Fernandes, T.M.,Burton, J.A.J.,Morgado, L.,van Wonderen, J.H.,Svistunenko, D.A.,Edwards, M.J.,Salgueiro, C.A.,Butt, J.N.,Clarke, T.A.
Tethered heme domains in a triheme cytochrome allow for increased electron transport distances.
Protein Sci., 33:e5200-e5200, 2024

PubMed Abstract: Decades of research describe myriad redox enzymes that contain cofactors arranged in tightly packed chains facilitating rapid and controlled intra-protein electron transfer. Many such enzymes participate in extracellular electron transfer (EET), a process which allows microorganisms to conserve energy in anoxic environments by exploiting mineral oxides and other extracellular substrates as terminal electron acceptors. In this work, we describe the properties of the triheme cytochrome PgcA from Geobacter sulfurreducens. PgcA has been shown to play an important role in EET but is unusual in containing three CXXCH heme binding motifs that are separated by repeated (PT) motifs, suggested to enhance binding to mineral surfaces. Using a combination of structural, electrochemical, and biophysical techniques, we experimentally demonstrate that PgcA adopts numerous conformations stretching as far as 180 Å between the ends of domains I and III, without a tightly packed cofactor chain. Furthermore, we demonstrate a distinct role for its domain III as a mineral reductase that is recharged by domains I and II. These findings show PgcA to be the first of a new class of electron transfer proteins, with redox centers separated by some nanometers but tethered together by flexible linkers, facilitating electron transfer through a tethered diffusion mechanism rather than a fixed, closely packed electron transfer chain.

PubMed: 39470321
DOI: 10.1002/pro.5200

Experimental method

X-RAY DIFFRACTION (1.9 Å)