Norio Murata

Control of excitation transfer in photosynthesis I. Light-induced change of chlorophyll a fluoresence in Porphyridium cruentum

The emission spectra of chlorophyll a in Porphyridium cruentum at liquid nitrogen temperature change on illumination of the sample before cooling. Preillumination of phycoerythrin decreases the yields of F684 and F695 and increases that of F-1. Pre-illumination of chlorophyll a does not significantly change the fluorescence yield. These facts indicate that the pre-illumination of pigment system II changes the efficiency of excitation transfer between chlorophyll a molecules. The effects of additional actinic illumination on the yield of F684 at room temperature are also examined. The actinic illumination of chlorophyll a has two opposing effects on the fluoresence yield, i.e., decrease and increase of fluorescence yield. The two effects can be distinguished by the difference in times of response towards the onset and end of actinic illumination. The former (fast, decreasing) effect can be explained in connection with the cooperation of the two pigment systems through the photosynthetic electron transport. The latter (slow, increasing) effect is thought to reflect the change in efficiency of excitation transfer, as mentioned above concerning the fluorescence yields at liquid nitrogen temperature. The presence of a light-induced control for the efficient utilization of the absorbed light energy in photosynthesis is suggested.

Control of excitation transfer in photosynthesis. II. Magnesium ion-dependent distribution of excitation energy between two pigment systems in spinach chloroplasts

1. 1. Effects of metal ions on the yields of chlorophyll a fluorescence were investigated in spinach chloroplasts. At room and liquid-nitrogen temperatures, addition of Mg2+ increased the yields of two emissions of chlorophyll a, having peaks at 684 and 695 nm which were emitted from pigment system II and decreased the yield of another emission of chlorophyll a at about 735 nm which was emitted from pigment system I. Mg2+ also changed the pattern of the fluorescence induction at room temperature to increase the variable component of fluorescence. 2. 2. Effects of Mg2+ on the quantum yields of the two photoreactions were investigated in a region of weak light intensities. Mg2+ accelerated the rate of photoreaction II measured by the Hill reaction with 2,6-dichlorophenolindophenol and depressed the rate of photoreaction I measured by the NADP+ reduction in the presence of reduced 2,6-dichlorophenolindophenol and 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea. 3. 3. These facts indicate that Mg2+ controls the distribution of excitation energy between the two pigment systems and that the control consists mainly in change in rate of excitation transfer from the bulk chlorophyll a molecules in pigment system II to those in pigment system I; namely, Mg2+ suppresses the spillover of excitation energy from pigment system II to pigment system I.

Role of the 33-kDa polypeptide in preserving Mn in the photosynthetic oxygen-evolution system and its replacement by chloride ions

Treatment of Photosystem II particles from spinach chloroplasts with Triton X‐100 with 2.6 M urea in the presence of 200 mM NaCl removed 3 polypeptides of 33 kDa, 24 kDa and 18 kDa, but left Mn bound to the particles. The (urea + NaCl)‐treated particles could evolve oxygen in 200 mM, but not in 10 mM NaCl. Mn was gradually released with concomitant loss of oxygen‐evolution activity in 10 mM NaCl but not in 200 mM Cl−. The NaCl‐treated particles, which contained Mn and the 33‐kDa polypeptide but not the 24‐kDa and 18‐kDa polypeptides, did not lose Mn or oxygen‐evolution activity in 10 mM NaCl. These observations suggest that the 33‐kDa polypeptide maintains the binding of Mn to the oxygen‐evolution system and can be functionally replaced by 200 mM Cl−.

Calcium ions can be substituted for the 24-kDa polypeptide in photosynthetic oxygen evolution

Photosystem II particles were prepared from spinach chloroplasts with Triton X‐100, and treated with 1.0 M NaCl to remove polypeptides of 24 kDa and 18 kDa and to reduce the photosynthetic oxygen‐evolution activity by about half. Oxygen‐evolution activity was restored almost to the original level with 10 mM Ca2+, in a similar manner to the rebinding of 24‐kDa polypeptide. Other cations such as magnesium, sodium and manganese ions could not restore any oxygen‐evolution activity. These observations, together with a kinetic analysis, suggest that Ca2+ can be substituted for the 24‐kDa polypeptide in photosynthetic oxygen evolution in Photosystem II particles.

Heat inactivation of oxygen evolution in Photosystem II particles and its acceleration by chloride depletion and exogenous manganese

Abstract Heat inactivation of oxygen evolution by isolated Photosystem II particles was accelerated by Cl − depletion and exogenous Mn 2+ . Weak red light also accelerated heat inactivation. Heat treatment released the 33, 24 and 18 kDa proteins and Mn from the Photosystem II particles. The protein release was stimulated by Cl − depletion and exogenous Mn 2+ , and the Mn release was also stimulated by Cl − depletion. A 50% loss of Mn corresponded to full inactivation of oxygen evolution, whereas no direct correlation seemed to exist between the loss of any one protein and inactivation of oxygen evolution. Removal of the 24 and 18 kDa proteins from photosystem II particles only slightly decreased the heat stability of oxygen evolution.

Stoichiometry of components in the photosynthetic oxygen evolution system of Photosystem II particles prepared with Triton X-100 from spinach chloroplasts

Abstract The stoichiometry of the proteins of the photosynthetic oxygen evolution system and of the electron transport components in Photosystem II particles prepared with Triton X-100 from spinach chloroplasts were determined. Per about 220 chlorophyll molecules, there were one reaction center II, one molecule each of the 33, 24 and 18 kDa proteins, four Mn atoms, two cytochromes b -559 (one high-potential, the other low-potential), and 3.5 plastoquinone-9 molecules, but practically no cytochrome b -563, cytochrome f , phylloquinone, α-tocopherol or α-tocopherylquinone.

Extrinsic membrane proteins in the photosynthetic oxygen-evolving complex

Abstract Preparations of photosystem II membranes, in which the active site of oxygen evolution is exposed to the bulk aqueous phase, have facilitated biochemical studies of the photosynthetic oxygen-evolving complex (the photosynthetic water oxidase complex). Described here are photosystem II membrane preparations highly active in oxygen evolution and three extrinsic membrane proteins for which the molecular properties and functions in oxygen evolution have been characterized.

Partial disintegration and reconstitution of the photosynthetic oxygen evolution system. Binding of 24 kilodalton and 18 kilodalton polypeptides

Abstract Treatment with 1 M NaCl almost totally removed two polypeptides of 24 and 18 kDa from the Photosystem II particles of spinach chloroplasts and reduced the oxygen-evolution activity by about half. Both polypeptides were able to rebind to the NaCl-treated particles in a low-salt medium. The rebinding of the 24 kDa polypeptide showed a saturation curve whose maximum level was close to that naturally occurring in the untreated particles. In parallel with the amount of rebound 24 kDa polypeptide, the oxygen-evolution activity was recovered. The 18 kDa polypeptide bound to the NaCl-treated particles without saturation. When the 18 kDa polypeptide was added to the particles previously treated with NaCl and then supplemented with a saturating amount of 24 kDa polypeptide, there appeared, in addition to the binding without saturation, another binding of the 18 kDa polypeptide with saturation to a maximum level close to that naturally occurring in the untreated particles. The 18 kDa polypeptide did not restore the oxygen-evolution activity. These findings suggest that there are specific binding sites; one for the 24 kDa polypeptide located on the Photosystem II particles, and the other for the 18 kDa polypeptide on the 24 kDa polypeptide.

The function of 33-kDa protein in the photosynthetic oxygen-evolution system studied by reconstitution experiments

Abstract Treatment of Photosystem II particles with 1.2 M CaCl2 released three proteins of 33, 24 and 18 kDa of the photosynthetic oxygen evolution system, but left Mn bound to the particles as demonstrated by Ono and Inoue (Ono, T. and Inoue, Y. (1983) FEBS Lett. 164, 252–260). Oxygen-evolution activity of the CaCl2-treated particles was very low in a medium containing 10 mM NaCl as a salt, but could be restored by the 33-kDa protein. When the particles were incubated in 10 mM NaCl at 0°C, two of the four Mn atoms per oxygen-evolution system were released with concomitant loss of oxygen-evolution activity. The 33-kDa protein suppressed the release of Mn and the inactivation during the incubation. These findings from reconstitution experiments suggest that the 33-kDa protein acts to preserve Mn atoms in the oxygen-evolution system. The 33-kDa protein could be partially substituted by 100 or 150 mM Cl− for the preservation of the Mn and oxygen-evolution activity. The Mn in Photosystem II particles enhanced rebinding of the 33-kDa protein to the particles.

A RAPID AND EFFICIENT METHOD TO PREPARE CHLOROPHYLL A AND B FROM LEAVES

Abstract— Highly purified Chi a and b were prepared from spinach leaves in a short time by a combined use of the column chromatography with DEAE‐Sepharose CL‐6B and Sepharose CL‐6B. The former chromatography eliminated carotenoids, phaeophytin and chlorophyllide, and the latter chromatography efficiently separated Chi a and b.