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An Arabidopsis thaliana cDNA encoding PS II‐X, a 4.1 kDa component of photosystem II: a bipartite presequence mediates SecA/ΔpH‐independent targeting into thylakoids
Author(s) -
Robinson David,
Robinson Colin
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00658-8
Subject(s) - photosystem ii , arabidopsis thaliana , thylakoid , arabidopsis , component (thermodynamics) , complementary dna , oxygen evolving complex , chemistry , photosynthesis , biology , biochemistry , chloroplast , biophysics , gene , physics , mutant , thermodynamics
Higher plant photosystem II preparations contain a 4.1 kDa polypeptide (subunit X) associated with the oxygen‐evolving core complex. We describe the isolation of a cDNA encoding PS II‐X from Arabidopsis thaliana , in which the C‐terminal region is highly homologous to partially sequenced PS II‐X from wheat and spinach. The mature protein of 42 residues is preceded by a 74‐residue, bipartite presequence similar to those involved in the targeting of nuclear‐encoded thylakoid lumen proteins, although hydrophobicity analysis indicates the presence of a single transmembrane span in the mature protein. Moreover, import of pre‐PS II‐X into the thylakoid membrane of isolated chloroplasts is unaffected by inhibitors of either the Sec‐ or ΔpH‐dependent thylakoidal protein translocases, suggesting a spontaneous insertion mechanism. PS II‐X appears to be encoded as a mature protein by the plastid genome in the chlorophyll a + c ‐containing alga, Odontella sinensis . We thus propose that the thylakoid transfer signal of Arabidopsis pre‐PS II‐X represents a recent acquisition, in phylogenetic terms, compared with signals of Sec‐dependent lumenal proteins.