scholarly journals Characterization of the human multidrug resistance protein containing mutations in the ATP-binding cassette signature region

1997 ◽  
Vol 323 (3) ◽  
pp. 777-783 ◽  
Author(s):  
Éva BAKOS ◽  
Izabella KLEIN ◽  
Ervin WELKER ◽  
Katalin SZABÓ ◽  
Marianna MÜLLER ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Amino Acid ◽  
Atpase Activity ◽  
Single Amino Acid ◽  
Membrane Insertion ◽  
Atp Binding ◽  
Mdr1 Expression ◽  
And Function ◽  
Atp Binding Cassette

A number of mutants with single amino acid replacements were generated in the highly conserved ATP-binding cassette (ABC)-signature region (amino acids 531–543) of the N-terminal half of the human multidrug resistance (MDR1) protein. The cDNA variants were inserted into recombinant baculoviruses and the MDR1 proteins were expressed in Spodoptera frugiperda (Sf9) insect cells. The level of expression and membrane insertion of the MDR1 variants was examined by immunostaining, and MDR1 function was followed by measuring drug-stimulated ATPase activity. We found that two mutations, L531R and G534V, practically eliminated MDR1 expression; thus these amino acid replacements seem to inhibit the formation of a stable MDR1 protein structure. The MDR1 variants G534D and I541R were expressed at normal levels with normal membrane insertion, but showed a complete loss of drug-stimulated ATPase activity, while mutant R538M yielded full protein expression but with greatly decreased ATPase activity. Increasing the ATP concentration did not restore MDR1 ATPase activity in these variants. Some amino acid replacements in the ABC-signature region (K536I, K536R, I541T and R543S) affected neither the expression and membrane insertion nor the ATPase function of MDR1. We found no alteration in the drug-sensitivity of ATP cleavage in any of the MDR1 variants that had measurable ATPase activity. These observations suggest that the ABC-signature region is essential for MDR1 protein stability and function, but alterations in this region do not seem to modulate MDR1–drug interactions directly.

scholarly journals Evolutionary Analyses of ABC Transporters of Dictyostelium discoideum

2002 ◽  
Vol 1 (4) ◽  
pp. 643-652 ◽  
Author(s):  
Christophe Anjard ◽  
William F. Loomis
Keyword(s):  
Amino Acid ◽  
Dictyostelium Discoideum ◽  
Abc Transporters ◽  
Sequence Homology ◽  
Genome Project ◽  
The Other ◽  
Atp Binding ◽  
And Function ◽  
Insight Into ◽  
Atp Binding Cassette

ABSTRACT The ABC superfamily of genes is one of the largest in the genomes of both bacteria and eukaryotes. The proteins encoded by these genes all carry a characteristic 200- to 250-amino-acid ATP-binding cassette that gives them their family name. In bacteria they are mostly involved in nutrient import, while in eukaryotes many are involved in export. Seven different families have been defined in eukaryotes based on sequence homology, domain topology, and function. While only 6 ABC genes in Dictyostelium discoideum have been studied in detail previously, sequences from the well-advanced Dictyostelium genome project have allowed us to recognize 68 members of this superfamily. They have been classified and compared to animal, plant, and fungal orthologs in order to gain some insight into the evolution of this superfamily. It appears that many of the genes inferred to have been present in the ancestor of the crown organisms duplicated extensively in some but not all phyla, while others were lost in one lineage or the other.

scholarly journals The MexR Repressor of the mexAB-oprM Multidrug Efflux Operon in Pseudomonas aeruginosa: Characterization of Mutations Compromising Activity

2002 ◽  
Vol 184 (15) ◽  
pp. 4308-4312 ◽  
Author(s):  
Lateef Adewoye ◽  
Ainsley Sutherland ◽  
Ramakrishnan Srikumar ◽  
Keith Poole
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Multidrug Resistance ◽  
Amino Acid ◽  
Dna Binding ◽  
Single Amino Acid ◽  
Multidrug Efflux ◽  
Resistance Phenotype

ABSTRACT Mutations in mexR yield a multidrug resistance phenotype in nalB mutants of Pseudomonas aeruginosa as a result of derepression of the mexAB-oprM multidrug efflux operon. MexR produced by several nalB strains carried single amino acid changes that compromised MexR stability or its ability to dimerize. Changes at residues L95 and R21, however, produced a stable MexR protein capable of dimerization and, thus, likely compromised DNA binding.

Increased plasma plant sterol concentrations and a heterozygous amino acid exchange in ATP binding cassette transporter ABCG5: A case report

2011 ◽  
Vol 54 (4) ◽  
pp. e458-e460 ◽  
Author(s):  
Sylvia Keller ◽  
Danielle Prechtl ◽  
Charalampos Aslanidis ◽  
Uta Ceglarek ◽  
Joachim Thiery ◽  
...  
Keyword(s):  
Case Report ◽  
Amino Acid ◽  
Plant Sterol ◽  
Atp Binding ◽  
Amino Acid Exchange ◽  
Atp Binding Cassette Transporter ◽  
Acid Exchange ◽  
Plasma Plant ◽  
Atp Binding Cassette

Functional and Structural Characterization of Acquired Pan-Aminoglycoside Resistance 16S rRNA Methyltransferase NpmB1

2021 ◽  
Author(s):  
Akito Kawai ◽  
Masahiro Suzuki ◽  
Kentaro Tsukamoto ◽  
Yusuke Minato ◽  
Yohei Doi
Keyword(s):  
Amino Acid ◽  
16S Rrna ◽  
Amino Acid Identity ◽  
Single Amino Acid ◽  
Aminoglycoside Resistance ◽  
E Coli ◽  
The United Kingdom ◽  
Amino Acid Variant ◽  
A Site

Post-translational methylation of the A site of 16S rRNA at position A1408 leads to pan-aminoglycoside resistance encompassing both 4,5- and 4,6-disubstituted 2-deoxystreptamine (DOS) aminoglycosides. To date, NpmA is the only acquired enzyme with such function. Here, we present function and structure of NpmB1 whose sequence was identified in Escherichia coli genomes registered from the United Kingdom. NpmB1 possesses 40% amino acid identity with NpmA1 and confers resistance to all clinically relevant aminoglycosides including 4,5-DOS agents. Phylogenetic analysis of NpmB1 and NpmB2, its single amino acid variant, revealed that the encoding gene was likely acquired by E. coli from a soil bacterium. The structure of NpmB1 suggests that it requires a structural change of the β6/7 linker in order to bind to 16S rRNA. These findings establish NpmB1 and NpmB2 as the second group of acquired pan-aminoglycoside resistance 16S rRNA methyltransferases.

Biochemical and genetic characterization of a yeast TFIID mutant that alters transcription in vivo and DNA binding in vitro

1992 ◽  
Vol 12 (5) ◽  
pp. 2372-2382
Author(s):  
K M Arndt ◽  
S L Ricupero ◽  
D M Eisenmann ◽  
F Winston
Keyword(s):  
Amino Acid ◽  
Dna Binding ◽  
Direct Repeat ◽  
Single Amino Acid ◽  
Wild Type ◽  
Dna Binding Specificity ◽  
Selection For

A mutation in the gene that encodes Saccharomyces cerevisiae TFIID (SPT15), which was isolated in a selection for mutations that alter transcription in vivo, changes a single amino acid in a highly conserved region of the second direct repeat in TFIID. Among eight independent spt15 mutations, seven cause this same amino acid change, Leu-205 to Phe. The mutant TFIID protein (L205F) binds with greater affinity than that of wild-type TFIID to at least two nonconsensus TATA sites in vitro, showing that the mutant protein has altered DNA binding specificity. Site-directed mutations that change Leu-205 to five different amino acids cause five different phenotypes, demonstrating the importance of this amino acid in vivo. Virtually identical phenotypes were observed when the same amino acid changes were made at the analogous position, Leu-114, in the first repeat of TFIID. Analysis of these mutations and additional mutations in the most conserved regions of the repeats, in conjunction with our DNA binding results, suggests that these regions of the repeats play equivalent roles in TFIID function, possibly in TATA box recognition.

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