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Structural characterizations of the chloroplast translocon protein Tic110
Author(s) -
Tsai JiaYin,
Chu ChiungChih,
Yeh YiHung,
Chen LihJen,
Li Hsoumin,
Hsiao ChwanDeng
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12249
Subject(s) - translocon , small angle x ray scattering , transit peptide , crystallography , transmembrane domain , transmembrane protein , n terminus , biophysics , chloroplast , chemistry , scattering , membrane protein , peptide sequence , membrane , biochemistry , biology , physics , plastid , receptor , optics , gene
Summary Tic110 is a major component of the chloroplast protein import translocon. Two functions with mutually exclusive structures have been proposed for Tic110 : a protein‐conducting channel with six transmembrane domains and a scaffold with two N ‐terminal transmembrane domains followed by a large soluble domain for binding transit peptides and other stromal translocon components. To investigate the structure of Tic110 , Tic110 from C yanidioschyzon merolae ( C m T ic110) was characterized. We constructed three fragments, C m T ic110 A , C m T ic110 B and C m T ic110 C , with increasing N ‐terminal truncations, to perform small‐angle X ‐ray scattering ( SAXS ) and X ‐ray crystallography analyses and D ali structural comparison. Here we report the molecular envelope of C m T ic110 B and C m T ic110 C determined by SAXS , and the crystal structure of C m T ic110 C at 4.2 Å. Our data indicate that the C ‐terminal half of C m T ic110 possesses a rod‐shaped helix‐repeat structure that is too flattened and elongated to be a channel. The structure is most similar to the HEAT ‐repeat motif that functions as scaffolds for protein–protein interactions.