Abstract
Acaryochloris spp. are unique cyanobacteria that differ from the majority of photosynthetic organisms by having Chl d as the major pigment. We reported the isolation of PS II core complex from A. marina MBIC 11017 and confirmed the special pair comprised Chl d homodimer in 2007. In our previous work, the Chl d content per two pheophytin a was ca. 55; the presence of CP43' may be a primary reason for why a higher level of pigment contents than expected. In this study, we modified a purification procedure and almost completely removed CP43'. In the current PS II core complexes, the number of Chl d and Chl a per two Phe a molecules was estimated to be 29.6 ± 1.2 and 1.9 ± 0.1, respectively. These values are dramatically lower than the previous report. The absorption spectrum of A. marina PS II at 80 K showed the presence of a new short-wavelength component at 672 nm, probably Chl a, which was detected by a decrease in antenna pigments. There are several enigmas in PS II of A. marina (e.g. redox potential of primary acceptor, localization and function of Chl a). This improved preparation will be suitable for further study.
