title: Twin plastocyanin dimorphism in tobacco.
abstract: Two iso-plastocyanin fractions, oxidized b-plastocyanin, PCb(II) and reduced a-plastocyanin, PCa(I), have been isolated from whole tobacco leaves by conventional chromatography on DEAE-cellulose. The isoelectric points of PCa and PCb at 10 degrees C were found to be 3.99 and 3.97, respectively. When the primary structures were analysed, a microheterogeneity within both PCa and PCb was observed. By appropriate peptide arrangements the amino-acid sequences of two PCa (PCa' and PCa") and two PCb (PCb' and PCb") have been differentiated. All four sequences contain 99 amino-acid residues. PCa' and PCa" differ in one position, where Ser-58 in PCa' is replaced by Pro in PCa".PCb' and PCb" differ in three positions, where Gly-65, Thr-81 and Ala-85 in PCb' are replaced by Ala, Ser and Ser in PCb", respectively. PCa (PCa'/PCa") generally differs from PCb (PCb'/PCb") in three positions, where Val-52, Glu-61 and Tyr-62 in PCa'/PCa" are replaced by Ala, Asp and Leu in PCb'/PCb", respectively. Fluorescence spectra of oxidized tobacco PCa and PCb have been characterized with an emission-maximum position at around 340 nm. The presence of one extra tyrosyl (Tyr-62) in PCa results in a weak increase of the maximal intensity in conjunction with a slight blue-shift of the maximum position.
authors.affiliation: Central Laboratory of Biophysics, Bulgarian Academy of Sciences, Sofia.
authors.forename: M I
authors.initials: MI
authors.lastname: Dimitrov
authors.forename: A A
authors.initials: AA
authors.lastname: Donchev
authors.forename: T A
authors.initials: TA
authors.lastname: Egorov
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D007525:Isoelectric Focusing; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010947:Plants, Toxic; D010970:Plastocyanin / Q000737:chemistry* / Q000302:isolation & purification; D014026:Nicotiana / Q000737:chemistry*
chemical_list: D010970:Plastocyanin