I.M. Folea C.C. Jolley R. Kouril C.E. Lubner S. Lin D. Kolber Felisa Wolfe-Simon J.H. Golbeck E.J. Boekema P. Fromme D. Chauhan 2011 <p><span>Iron (Fe) availability is a major limiting factor for primary production in aquatic environments. Cyanobacteria respond to Fe deficiency by derepressing the&nbsp;</span><i>isiAB</i><span>&nbsp;operon, which encodes the antenna protein IsiA and flavodoxin. At nanomolar Fe concentrations, a PSI−IsiA supercomplex forms, comprising a PSI trimer encircled by two complete IsiA rings. This PSI−IsiA supercomplex is the largest photosynthetic membrane protein complex yet isolated. This study presents a detailed characterization of this complex using transmission electron microscopy and ultrafast fluorescence spectroscopy. Excitation trapping and electron transfer are highly efficient, allowing cyanobacteria to avoid oxidative stress. This mechanism may be a major factor used by cyanobacteria to successfully adapt to modern low-Fe environments.</span></p> application/pdf 10.1021/bi1009425 en American Chemical Society A novel photosynthetic strategy for adaptation to low-iron aquatic environments article