ABC-F Protein Research Articles

Detailed mutational analysis of Vga(A) interdomain linker: implication for antibiotic resistance specificity and mechanism.

Detailed mutational analysis examines the roles of individual residues of the Vga(A) linker in determining the antibiotic resistance phenotype. It defines a narrowed region of residues 212 to 220 whose composition determines the resistance specificity to lincosamides, pleuromutilins, and/or streptogramins A. From the analogy with the recently described function of the homologous ABC-F protein EttA as a translational factor, we infer that the Vga(A) linker interacts with the ribosome and directly or indirectly affects the binding of the respective antibiotic.

The ABC-F protein EttA gates ribosome entry into the translation elongation cycle

ABC-F proteins have evaded functional characterization even though they comprise one of the most widely distributed branches of the ATP-binding cassette (ABC) superfamily. Herein, we demonstrate that YjjK, the most prevalent eubacterial ABC-F protein, gates ribosome entry into the translation elongation cycle through a nucleotide-dependent interaction sensitive to ATP/ADP ratio. Accordingly, we rename this protein Energy-dependent Translational Throttle A (EttA). We determined the crystal structure of Escherichia coli EttA and used it to design mutants for biochemical studies, including enzymological assays of the initial steps of protein synthesis. These studies suggest that EttA may regulate protein synthesis in energy-depleted cells, which have a low ATP/ADP ratio. Consistent with this inference, ΔettA cells exhibit a severe fitness defect in long-term stationary phase. These studies demonstrate that an ABC-F protein regulates protein synthesis via a novel mechanism sensitive to cellular energy status.

Sequence analysis of twin ATP binding cassette proteins involved in translational control, antibiotic resistance, and ribonuclease L inhibition

Genome sequencing has identified open reading frames which belong to the ATP binding cassette (ABC) transporter family, but which are unlikely to be involved in transport phenomena. These frequently contain a pair of nucleotide binding domains (NBD) with no associated transmembrane domains. The functions of many of these twin-NBD proteins remain unknown. In this manuscript, sequence analysis has been employed to analyse two families of twin-NBD proteins, ABCE and ABCF. The ABCE proteins, postulated to be inhibitors of RNase L, are identified by two potential Fe–S metal-binding domains in addition to two NBDs. Surprisingly, ABCE homologues are identified in numerous species which apparently lack an RNase L, questioning the proposed function of these proteins. The ABCF proteins can be sub-divided into more than a dozen sub-classes. Intriguingly, sequence similarity is shown between eukaryotic ABCF proteins, which are involved in translation initiation and elongation, and prokaryotic ABCF proteins which are implicated in resistance to macrolide inhibitors of protein synthesis.