Molecular architecture of photosynthetic membranes in Rhodobacter sphaeroides: the role of PufX
AUTOR(ES)
Siebert, C Alistair
FONTE
Nature Publishing Group
RESUMO
The effects of the PufX polypeptide on membrane architecture were investigated by comparing the composition and structures of photosynthetic membranes from PufX+ and PufX− strains of Rhodobacter sphaeroides. We show that this single polypeptide profoundly affects membrane morphology, leading to highly elongated cells containing extended tubular membranes. Purified tubular membranes contain helical arrays composed solely of dimeric RC–LH1–PufX (RC, reaction centre; LH, light harvesting) complexes with apparently open LH1 rings. PufX− cells contain crystalline membranes with a pseudo-hexagonal packing of monomeric core complexes. Analysis of purified complexes by electron microscopy and atomic force microscopy shows that LH1 and PufX form a continuous ring of protein around each RC. A model of the tubular membrane is presented with PufX located adjacent to the stained region created by a vacant LH1β. This arrangement, coupled with a flexible ring, would give the RC QB site transient access to the interstices in the lattice, which might be of functional importance. We discuss the implications of our data for the export of quinol from the RC, for eventual reduction of the cytochrome bc1 complex.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=381000Documentos Relacionados
- Studies on the expression of the pufX polypeptide and its requirement for photoheterotrophic growth in Rhodobacter sphaeroides.
- Photoresponses in Rhodobacter sphaeroides: role of photosynthetic electron transport.
- The long-range supraorganization of the bacterial photosynthetic unit: A key role for PufX
- The Q gene of Rhodobacter sphaeroides: its role in puf operon expression and spectral complex assembly.
- Oxygen-insensitive synthesis of the photosynthetic membranes of Rhodobacter sphaeroides: a mutant histidine kinase.