Localization and Characterization of a Novel 20 kDa Polypeptide in the Chloroplast of the Green AlgaDunaliella salina

摘要

Recent work with the green algaDunaliella salinashowed the presence of a˜20 kDa chloroplast protein that was recognized by polyclonal antibodies raised against the isolated LHC-II Webb M.R. and Melis A. (1995)Plant Physiol. 107: 885. In this report, a characterization of the˜20 kDa polypeptide is presented. It is shown that it is localized in the chloroplast envelope membrane ofD. salina. The abundance of this protein is constant on a per cell basis and independent of the light regime during cell growth. The˜20 kDa polypeptide is easily degraded to a˜19 kDa product during sample preparation. A limited amino acid sequence of 21 residues from the free N-terminus of the˜19 kDa product was obtained. On the basis of this partial sequence, it was concluded that the˜20 kDa polypeptide is not a degradation product of a known LHC-II but rather a novel protein. The˜20kDa polypeptide did not cross-react with antibodies raised against theCbr(carotene biosynthesis-related) gene product and showed a different electrophoretic mobility from the latter. Light-shift experiments suggest that the˜20 kDa polypeptide is not an ELIP (early light-inducible protein). Possible functions of the˜20 kDa protein are d