Chlorellavirus-Proteine: I. Die Hüllprotein-Genfamilie II. Ein primitiver Kaliumkanal
Chlorella Virus Proteins: I. The Coat Protein Gene Family II. A Primitive Potassium Channel
von Barbara Ebert
Datum der mündl. Prüfung:2000-01-25
Erschienen:2000-11-07
Betreuer:PD Dr. Gerhard Thiel
Gutachter:Prof. Dr. Dietrich Gradmann
Gutachter:PD Dr. Gerhard Thiel
Dateien
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Description:Dissertation
Zusammenfassung
Englisch
Part I: The coat protein gene family Coat proteins play a decisive role in viral host recognition. They interact specifically with structures of the cell surface and mediate viral adherence. Chlorella virus isolates are highly host specific and are grouped accordingly: Pbi viruses infect Chlorella strain Pbi (isolated from Paramecium bursaria cells collected in Göttingen, Germany), NC64A viruses infect Chlorella strain NC64A (isolated from Paramecium bursaria cells collected in North Carolina, USA) and HVCV viruses infect Chlorella strains isolated from the fresh water polyp Hydra viridis. The following similarities between the Pbi virus CVG-1 and members of the NC64A viruses are established: 1) The major coat protein of CVG-1, Vp49, is similar in size and dimerization to the respective proteins of the NC64A viruses. 2) The corresponding major coat protein gene is part of a gene family with at least two more members. 3) Amino acid sequences of the three identified reading frames are homologous to sequences of the coat protein gene family of the NC64A virus strain PBCV-1. The corresponding amino acid sequences of Pbi viruses and NC64A viruses examined show - with one exception a divergence of about 25 %. Taking into account that corresponding genes among the NC64A viruses are almost identical, this divergence supports the original grouping of the NC64A and Pbi viruses according to host specificity. The virus strains clearly have evolved separately for some time, probably parallel to their respective host strains, endosymbiotic Chlorella strains Pbi and NC64A.Part II: A primitive potassium channel Kcv is a viral protein 94 amino acids in length, which posesses the typical properties of a potassium channel. Kcv induces a weakly voltage dependent, potassium-selective conductance in Xenopus laevis oocytes, which is inhibited by Ba2+ and amantadine, but not Cs+. Virus replication is inhibited in the same fashion, which indicates a role of Kcv in the viral life cycle. Thus, Kcv is the first potassium channel which is encoded by a virus. No proteins with structural analogy to Kcv have been found in other viral genomes. Moreover, Kcv ist the shortest functional potassium channel known to date. The structural and electrophysiological properties of Kcv justify its classification as a own class of potassium channel.
Keywords: Virus; Alga; ion channel; host specificity; Phycodnaviridae
Schlagwörter: Virus; Alge; Ionenkanal; Wirtsspezifität; Phycodnaviridae