The Escherichia coli ATP‐binding cassette (ABC) proteins

Abstract

SummaryThe recent completion of the Escherichia coli genome sequence (Blattner et al., 1997) has permitted an analysis of the complement of genomically encoded ATPbinding cassette (ABC) proteins. A total of 79 ABC proteins makes this the largest paralogous family of proteins in E. coli. These 79 proteins include 97 ABC domains (as some proteins include more than one ABC domain) and are components of 69 independent functional systems (as many systems involve more than one ABC domain). The ABC domains are often, but not exclusively, the energy-generating domains of multicomponent membrane-bound transporters. Thus, 57 of the 69 systems are ABC transporters, of which 44 are periplasmic-binding protein-dependent uptake systems and 13 are presumed exporters. The genes encoding these ABC transporters occupy almost 5% of the genome. Of the 12 systems that are not obviously transport related, the function of only one, the excision repair protein UvrA, is known. A phylogenetic analysis suggests that the majority of ABC proteins can be assigned to 10 subfamilies. Together with statistical and, importantly, biological evidence, this analysis provides insight into the evolution and function of the ABC proteins.

Membrane topology and mutational analysis of Escherichia coli CydDC, an ABC-type cysteine exporter required for cytochrome assembly

“…The number of positively and negatively charged residues within the periplasmic and CLs is indicated in boxes. The underlined sequences in the ATP-binding domain (C terminus) of both polypeptides show, respectively, the Walker sequence A, the linker peptide, the Walker sequence B and the conserved His residue common to ABC transporters (Linton & Higgins, 1998).…”

“…ABC transporters are central to many physiological processes, from bacteria to man, being responsible for solute uptake and for secretion of toxins, drugs and substrates that range from small ions to large proteins (for a review, see Schmitt & Tampe, 2002). The genome of E. coli encodes some 80 ABC transporters (Linton & Higgins, 1998), many of which, like CydDC, are poorly characterized. It was hypothesized that the substrate ('allocrite', i.e.…”

Coupling Factors in Macromolecular Type-IV Secretion Machineries

“…Secretion machineries spanning the cell membrane(s) are responsible for macromolecular transport. These systems can be classified into five types (I to V) and share the presence of proteins using nucleosyl triphosphate (NTP) hydrolysis as a transport driving force, except for the autotransporter system, which does not depend on NTP [1][2][3][4][5][6][7][8][9][10]. Over a dozen distinct families of protein translocating systems, mostly restricted to bacteria, have been characterised and classified [11,12].…”

Silica deposition and phenotypic changes to Thermus thermophilus cultivated in the presence of supersaturated silicia

“…Some ABC transporters and efflux pumps support the secretion of soluble factors and materials needed for colonization and biofilm formation, and can function as either importers or exporters with diverse substrates (Fath and Kolter, 1993;Linton and Higgins, 1998;Mah and O'toole, 2001;Vallet et al, 2001). Moreover, there have been numerous reports of biofilm-associated resistance to antibiotics and its possible mechanisms in gram-negative bacteria (Costerton et al, 1999;Drenkard, 2003;Lai et al, 2009).…”