Experimental evidence that the membrane-spanning helix of PufX adopts a bent conformation that facilitates dimerisation of the Rhodobacter sphaeroides RC-LH1 complex through N-terminal interactions

Journal Article · · Biochim. Biophys. Acta, Bioenerg.

DOI:https://doi.org/10.1016/j.bbabio.2010.10.003· OSTI ID:1065086

Ratcliffe, Emma C; Tunnicliffe, Richard B; Ng, Irene W; Adams, Peter G; Qian, Pu; Holden-Dye, Katherine; Jones, Michael R; Williamson, Michael P; Hunter, C Neil

The PufX polypeptide is an integral component of some photosynthetic bacterial reaction center-light harvesting 1 (RC–LH1) core complexes. Many aspects of the structure of PufX are unresolved, including the conformation of its long membrane-spanning helix and whether C-terminal processing occurs. In the present report, NMR data recorded on the Rhodobacter sphaeroides PufX in a detergent micelle confirmed previous conclusions derived from equivalent data obtained in organic solvent, that the α-helix of PufX adopts a bent conformation that would allow the entire helix to reside in the membrane interior or at its surface. In support of this, it was found through the use of site-directed mutagenesis that increasing the size of a conserved glycine on the inside of the bend in the helix was not tolerated. Possible consequences of this bent helical structure were explored using a series of N-terminal deletions. The N-terminal sequence ADKTIFNDHLN on the cytoplasmic face of the membrane was found to be critical for the formation of dimers of the RC–LH1 complex. It was further shown that the C-terminus of PufX is processed at an early stage in the development of the photosynthetic membrane. A model in which two bent PufX polypeptides stabilise a dimeric RC–LH1 complex is presented, and it is proposed that the N-terminus of PufX from one half of the dimer engages in electrostatic interactions with charged residues on the cytoplasmic surface of the LH1α and β polypeptides on the other half of the dimer.

• Research Organization: Energy Frontier Research Centers (EFRC); Photosynthetic Antenna Research Center (PARC)
• Sponsoring Organization: USDOE SC Office of Basic Energy Sciences (SC-22)
• DOE Contract Number: SC0001035
• OSTI ID: 1065086
• Journal Information: Biochim. Biophys. Acta, Bioenerg., Journal Name: Biochim. Biophys. Acta, Bioenerg. Vol. 1807
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
solar (fuels)
photosynthesis (natural and artificial)
biofuels (including algae and biomass)
bio-inspired
charge transport
membrane
synthesis (novel materials)
synthesis (self-assembly)