Super-channel in bacteria: structural and functional aspects of a novel biosystem for the import and depolymerization of macromolecules.
Cells of Sphingomonas sp. A1 directly incorporate a macromolecule, alginate, into the cytoplasm through a biosystem, super-channel, consisting of a pit on the cell surface, alginate-binding proteins in the periplasm, and an ATP-binding cassette transporter in the inner membrane. The alginate is finally depolymerized into constituent monosaccharides by polysaccharide lyases present in the cytoplasm. The fundamental frame of the biosystem for alginate transport, and the functions of the pit, binding proteins, and ABC transporter have already been reviewed together with those of alginate-depolymerization processes [Hashimoto et al., J. Biosci. Bioeng., 87, 123-136 (1999)]. In this review, we have attempted to demonstrate the three-dimensional structure and evolution features of the super-channel, and alginate-depolymerization processes by using information obtained mainly through genomics, proteomics, and X-ray crystallography.
Hashimoto
Wataru
W
Laboratory of Basic and Applied Molecular Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
Yamasaki
Masayuki
M
Itoh
Takafumi
T
Momma
Keiko
K
Mikami
Bunzo
B
Murata
Kousaku
K