Structural basis for the PufX-mediated dimerization of bacterial photosynthetic core complexes.
In Rhodobacter (Rba.) sphaeroides, the subunit PufX is involved in the dimeric organization of the core complex. Here, we report the 3D reconstruction at 12 A by cryoelectron microscopy of the core complex of Rba. veldkampii, a complex of approximately 300 kDa without symmetry. The core complex is monomeric and constituted by a light-harvesting complex 1 (LH1) ring surrounding a uniquely oriented reaction center (RC). The LH1 consists of 15 resolved alpha/beta heterodimers and is interrupted. Within the opening, PufX polypeptide is assigned at a position facing the Q(B) site of the RC. This core complex is different from a dissociated dimer of the core complex of Rba. sphaeroides revealing that PufX in Rba. veldkampii is unable to dimerize. The absence in PufX of Rba. veldkampii of a G(31)XXXG(35) dimerization motif highlights the transmembrane interactions between PufX subunits involved in the dimerization of the core complexes of Rhodobacter species.
Busselez
Johan
J
Institut Curie, UMR-CNRS 168, 11 rue Pierre et Marie Curie, F-75231 Paris Cedex 05, France.
Cottevieille
Magali
M
Cuniasse
Philippe
P
Gubellini
Francesca
F
Boisset
Nicolas
N
Lévy
Daniel
D
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D019281:Dimerization; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010788:Photosynthesis; D011487:Protein Conformation; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins