[Redox potentials of some metalloproteins]. / Okislitel'no-vosstanovitel'nye potentsialy nekotorykh metalloprotendov.

The standard redox potentials of soluble cytochromes c isolated from the green alga Chlorella and the blue-green algae Spirulina and Aphanezomenon were determined by potentiometric titration and found to be equal to +380 mB, +330 mB and +357 AB, respectively. The standard redox potentials of plastocyanin preparations from Pisum sativum and Atriplex leaves were also determined and found close to those of soluble cytochromes c, i. e. +395 mB and +375 mB, respectively. The metalloproteins studied were shown to belong to monoelectron carriers operating at the donor sites of photosystem I.

[Effect of metalloproteins on the photochemical activity of chloroplasts treated with polyene antibiotics]. / Deistvie metalloproteidov na fotokhimicheskuiu aktivnost' khloroplastov, obrabotannykh polienovymi antibiotikami

The effects of various metall-containing proteins (plastocyanin, plantacyanin, azurine and cytochromes of the f type) on the activity of photosystem I of chloroplasts, treated with polyene antibiotics, were studied. The inhibiting effect of the polyenes, surgumycin and philipin, was completely removed by an addition of copper-containing protein plastocyanin. No similar effect was exerted by other Cu-containing proteins--azurine and plantacyanin. The cytochromes of the f type isolated from the green algae chlorella, blue-green algae spiruline and aphanezomenone, having different electrophoretic properties, restored the activity of photosystem I of chloroplasts incubated with antibiotics in a different degree. Acid cytochrome f of chlorella restored the activity by 80--100%; less acid cytochrome f from spiruline-only by 50%. The least restoring effect was exerted by aphanezomenone cytochrome, which possesses some basic properties. The chloroplasts treatment with surgumycin did not affect the isolation of the terminal enzyme of the chloroplast electron-transporting chain of ferredoxin--NADP--reductase. Possible environment of plastocyanin in the chloroplast membrane and the mechanism of photosystem I restoration are discussed.

[Cytochrome f from Chlorella pyrenoidosa Pringsheim 82 T]. / Tsitokhrom f chlorella pyrenoidosa pringsheim l 821

Cytochrome of the f type was isolated from the thermophilous autotrophic strain Chlorella pyrenoidosa Pringsheim 82T and purified on Sephadex G-75. The isolation procedure allowed a simultaneous production of glutamate dehydrogenase isoenzymes. From 100 g of Chlorella wet paste 100 to 120 nM of electrophoretically unicomponent protein with a molecular weight of 12,000 to 13,000 were isolated. The Chlorella cytochrome had an absorption spectrum in the visible light that was typical of the f type cytochromes.