Crystal structure of mistletoe lectin I from Viscum album.

The crystal structure of the ribosome-inactivating protein (RIP) mistletoe lectin I (ML-I) from Viscum album has been solved by molecular replacement techniques. The structure has been refined to a crystallographic R-factor of 24.5% using X-ray diffraction data to 2.8 A resolution. The heterodimeric 63-kDa protein consists of a toxic A subunit which exhibits RNA-glycosidase activity and a galactose-specific lectin B subunit. The overall protein fold is similar to that of ricin from Ricinus communis; however, unlike ricin, ML-I is already medically applied as a component of a commercially available misteltoe extract with immunostimulating potency and for the treatment of human cancer. The three-dimensional structure reported here revealed structural details of this pharmaceutically important protein. The comparison to the structure of ricin gives more insights into the functional mechanism of this protein, provides structural details for further protein engineering studies, and may lead to the development of more effective therapeutic RIPs.

[Crystallization of three multiple forms of transketolase from baker's yeast]. / Kristallizatsiia trekh mnozhestvennykh form transketolazy iz pekarskikhdrozhzhei.

Three forms of baker's yeast transketolase have been revealed. These forms differed in thermal stability and elution profiles during chromatography on a phosphocellulose column and migrated with identical rates during electrophoresis in the presence of sodium dodecyl sulfate. The same forms in yeast, pig and rat liver and in different organs and tissues of the rabbit were found to be similar in their thermal stability and chromatographic properties. The relative amounts of the forms appeared to depend on the physiological state of the organism. Crystals of the three pure forms were grown using ammonium sulfate as the precipitating agent. These crystals differed morphologically and by stability upon storage. The possibility of interconversion of the transketolase forms is discussed.

Morphological differences in crystals of multiple forms of yeast transketolase.

Monocrystals of three individual multiple forms of yeast transketolase (A, B and C) differing in their thermostability have been obtained. Ammonium sulfate was used as a precipitating agent. Crystals of the mentioned forms were found to possess different morphology and stability during storage. Single crystals growing from the enzyme form C within 4-7 days were subsequently destroyed. Simultaneously, in the preparation, microcrystals started to grow in a great number. They were found to correspond morphologically to crystals obtained from transketolase A. A possibility of interconversions of the enzyme forms in sequence C----A----B is discussed.

[Physico-chemical characteristics of catalases from Micrococcus sp. n]. / Fiziko-khimicheskie kharakteristiki katalaz iz Micrococcus sp. n.

The physico-chemical properties of heme-containing and non-heme catalases isolated from the cell culture of Micrococcus sp. n. grown under intensive aeration were studied. The enzyme preparations were homogenous during polyacrylamide disc electrophoresis. The spectral and functional properties of the enzymes (e. g. specific activity, subunit molecular weight, quaternary structure, amino acid composition, immunoprecipitability, N-terminal amino acid sequences) were investigated. Monocrystals of non-heme catalase applicable for an X-ray analysis were grown and examined by X-ray spectroscopy. Both enzymes were stable upon storage in 40% ammonium sulfate for 2 months and resistant to lyophylization without any significant loss of their activity. Non-heme catalase is apparently an independent enzyme which is not derived from heme-containing catalase via dissociation, limited proteolysis or heme cleavage.

[Separation of leghemoglobin from the nodules of lupine, Lupinus luteus L., into components]. / Razdelenie na komponenty leggemoglobina iz kluben'kov liupina Lupinus luteus L

The crude leghaemoglobin suspension from root nodules of yellow lupine (Lupinus luteus L.) was separated into five fractions: I, IIa and IIb, IIIa and IIIb using the chromatography on DEAE-cellulose (numbered following the elution order). The visible absorption spectra show that fractions I, IIa and IIIa are met-leghaemoglobins while IIb and IIIb are oxy-forms. IIb and IIIb were converted to IIa and IIIa respectively when oxidized with potassium ferricyanide. The determination of two first N-terminal amino acids confirms the identity of pairs IIa-IIb and IIIa-IIIb. Three components of leghaemoglobin were obtained having the following N-terminal amino acids: Gly-Val- (the first), Gly-Ala- (the second), Ala-Val- (the third). The molecular weights obtained by Archibald's method are 17 900, 17 600, 18 800 respectively. The second leghaemoglobin species which contains more than 50% of the starting protein mixture was used to grow crystals for X-ray study of the tertiary structure of this protein.