Backbone Dynamics of Reduced Plastocyanin from the Cyanobacterium Anabaena variabilis: Regions Involved in Electron Transfer Have Enhanced Mobility†,‡
journal contributionposted on 20.12.2002, 00:00 by Lixin Ma, Mathias A. S. Hass, Nanna Vierick, Søren M. Kristensen, Jens Ulstrup, Jens J. Led
The dynamics of the backbone of the electron-transfer protein plastocyanin from the cyanobacterium Anabaena variabilis were determined from the 15N and 13Cα R1 and R2 relaxation rates and steady-state [1H]−15N and [1H]−13C nuclear Overhauser effects (NOEs) using the model-free approach. The 13C relaxation studies were performed using 13C in natural abundance. Overall, it is found that the protein backbone is rigid. However, the regions that are important for the function of the protein show moderate mobility primarily on the microsecond to millisecond time scale. These regions are the “northern” hydrophobic site close to the metal site, the metal site itself, and the “eastern” face of the molecule. In particular, the mobility of the latter region is interesting in light of recent findings indicating that residues also on the eastern face of plastocyanins from prokaryotes are important for the function of the protein. The study also demonstrates that relaxation rates and NOEs of the 13Cα nuclei of proteins are valuable supplements to the conventional 15N relaxation measurements in studies of protein backbone dynamics.