文档介绍：a ABC Transporters
Andre´ Goffeau, Benoıˆt De Hertogh and Philippe V. Baret
Universite´ Catholique de Louvain, Louvain-la-Neuve, Belgium
The ABC proteins constitute the largest family of proteins. binding receptor, the cytoplasmic NDB, and the mem-
They are present in all living species from Archaea to Homo brane TMD are believed to have arisen from mon
sapiens. They make up to 4% of the full plement ancestral ABC transporter in which these three proteins
of bacteria such as Escherichia coli or Bacillus subtilis. Each were already present. However, during evolution, the
eukaryote genome contains several dozens of members (over sequence of the periplasmic solute-binding receptors
100 in the plant Arabidopsis thaliana). They are recognized by diverges more rapidly than that of the TMDs, while that
a consensus ATP-binding region of approximately 100 amino of NBDs is the least divergent. Thus, all NBDs
acids which include the two Walker A and B motifs are homologous, but this is not true for the TMDs or
passing a linker or C region (Figure 1). The ABC the receptors. Nevertheless, the ic clustering
proteins catalyze a wide variety of physiological functions, patterns in bacterial ABC from different species are
most (but not all) of which being related to transport. This generally the same for all three types of proteins, despite
article describes the major physiological and biochemical their variable rate of evolution.
functions as well as the structural properties of some of the The topology of some eukaryotic ABC effluxers can
best-known ABC transporters using examples from the yeast plex as additional TM spans occur in some
haromyces cerevisiae and Homo sapiens. systems (Figure 3) as well as extra cytoplasmic domains
of presumed regulatory function.
Topology
Phylogeny
Most, but not all, ABC proteins are ABC transporters.
Each of those molecules contains, or is associated to, one The different families of ABC proteins transport a wide
or two c