Sulfoquinovosyl diacylglycerol is required for dimerisation of the Rhodobacter sphaeroides reaction centre-light harvesting 1 core complex.
Biochem J
; 481(13): 823-838, 2024 Jul 03.
Article
em En
| MEDLINE
| ID: mdl-38780411
ABSTRACT
The reaction centre-light harvesting 1 (RC-LH1) core complex is indispensable for anoxygenic photosynthesis. In the purple bacterium Rhodobacter (Rba.) sphaeroides RC-LH1 is produced both as a monomer, in which 14 LH1 subunits form a C-shaped antenna around 1 RC, and as a dimer, where 28 LH1 subunits form an S-shaped antenna surrounding 2 RCs. Alongside the five RC and LH1 subunits, an additional polypeptide known as PufX provides an interface for dimerisation and also prevents LH1 ring closure, introducing a channel for quinone exchange that is essential for photoheterotrophic growth. Structures of Rba. sphaeroides RC-LH1 complexes revealed several new components; protein-Y, which helps to form the quinone channel; protein-Z, of unknown function and seemingly unique to dimers; and a tightly bound sulfoquinovosyl diacylglycerol (SQDG) lipid that interacts with two PufX arginine residues. This lipid lies at the dimer interface alongside weak density for a second molecule, previously proposed to be an ornithine lipid. In this work we have generated strains of Rba. sphaeroides lacking protein-Y, protein-Z, SQDG or ornithine lipids to assess the roles of these previously unknown components in the assembly and activity of RC-LH1. We show that whilst the removal of either protein-Y, protein-Z or ornithine lipids has only subtle effects, SQDG is essential for the formation of RC-LH1 dimers but its absence has no functional effect on the monomeric complex.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
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Rhodobacter sphaeroides
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Complexos de Proteínas Captadores de Luz
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Multimerização Proteica
Idioma:
En
Revista:
Biochem J
Ano de publicação:
2024
Tipo de documento:
Article
País de afiliação:
Reino Unido