PARENT SESSION

Symposium S3A Bacteriochlorophyll based antenna systems
Tuesday August 31st, 2004 10:20 AM-12:20 PM Room 511D
Chair: Neil Hunter
Co-Chair: Richard Cogdell

Solution structures of the LH1 and polypeptides from Rhodospirillum rubrum. Zheng-Yu Wang^*,1, Kazutaka Gokan¹, Masayuki Kobayashi¹, Tsunenori Nozawa¹, ¹ Department of Biomolecular Engineering, Graduate School of Engineering, Sendai, Japan

ABSTRACT- We have determined the solution structures of LH1 and polypeptides from wild-type purple photosynthetic bacterium Rhodospirillum(R.) rubrum using multidimensional NMR spectroscopy. The two polypeptides form stable helices in organic solution as revealed by circular dichroism. All backbone and most side chain NMR resonances were assigned using the ¹³C and ¹⁵N doubly labeled samples. Total of 430 and 510 NOEs were collected for the and polypeptides, respectively. Combining with the backbone torsion angle information and amide hydrogen-bonding restraints, ten lowest-energy structures were calculated and refined for each of the polypeptide. In contrast to a bent structure (two short helices joined by a flexible linker) previously reported for the LH1 polypeptide of Rhodobacter sphaeroides, both the and polypeptides of R. rubrum exhibit a long helical structure that is considered to correspond to the central transmembrane domain. Strong hydrogen bonds were identified for the backbone amide protons of the two polypeptides over the helical regions. The polypeptide revealed a long helical structure from Gln12 to Glu42 with a short helix near the N terminus, whereas the polypeptide had a single helical region from Ser9 to Leu41. The overall structural features of these polypeptides are very similar to those of the corresponding LH2 and polypeptides determined by X-ray crystallography.

KEY WORDS: membrane protein, bacterial light-harvesting, nmr structure