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Determination of whether the cysteines within the drug-binding pocket of P-gp were accessible to the aqueous medium by testing whether they could be labeled with charged thiol-reactive compounds is described. The results of this study indicate that regions of the drug-binding pocket are accessible to the aqueous medium.

Research has been conducted on the cystic fibrosis transmembrane conductance regulator (CFTR). The determination of the differences between the mature and immature CFTR structures has been conducted.

The secondary structure content of the components of coat protein were determined under both assembly and dissociating conditions using synchrotron radiation circular dichroism. The coat protein displayed no change in secondary structure content on assembly. On the other hand, isolated triskelia and hubs displayed a loss of helical content on assembly. Results are in agreement with a model for assembly that does not need the intertwining of triskelia.

A study on the 170 kDa plasma membrane glycoprotein called p-glycoprotein (P-gp) was conducted to investigate whether two forms of P-gp detected in the P-gp third cytoplasmic loop, that are both very similar polypeptides, are active and function as drug pumps. Results suggest that only one of the molecules is active and is able to interact with the other P-gp form. Further, this interaction is promoted by the presence of drug substrates.

All nine point mutations identified in cytoplasmic loops (CLs) 1 and 2 from patients with cystic fibrosis were reconstructed in the expression vector pcDNA3-cystic fibrosis transmembrane conductance regulator (CFTR). These were then expressed temporarily in COS-1 and HEK-293 cells and stably in Chinese hamster ovary cells. Findings indicated that misprocessing of the channel induces the disease symptoms in the patients. The N-terminal CLs seem to have no effect on the anion translocation pathway of CFTR.

Analysis of the functions of the amino acids in the transmembrane segment 6 of human P-glycoprotein during drug transport by using mutant cDNAs expressed in mouse NIH 3T3 cells reveals that four distinct mutations regulate the substrate specificity and the resistance to cytotoxin drugs of P-glycoprotein. Mutant Val338 to Ala increases resistance to colchicine and decreases that to vinblastine, while mutant Gly341 to Val induces little resistance to doxorubicin or colchicine. Mutant Ala342 to Leu decreases the resistance of the P-glycoprotein to all the three drugs, while mutant Ser344 to Cys, Thr, Ala or Tyr completely eliminates the drug resistance.

A study was conducted to identify and characterize rat cDNAs encoding possible mammalian homologues of the yeast secretory pathway Ca2+ pump. mRNAs corresponding to the cDNA were observed in all subject tissues which indicates mRNA's housekeeping function. Further comparative analyses supported the hypothesis that the alternatively spliced mRNAs are mammalian homologues of the yeast secretory pathway calcium pump.

Studies were conducted for the BCP homologue of Burkholderia cenocepacia (BcBCP) and bacterioferritin comigratory protein (BCP) of Escherichia coli to clarify the catalytic mechanism related to the active and resolving cysteine and unresolving cysteine of BCP peroxiredins. The characterization supported the subdivision of the BCP family of peroxiredoxins into two classes based on their catalytic activity.

A study was conducted to examine the effect of correctors and the [Delta]F508 mutation on interactions between the halves of cystic fibrosis transmembrane conductance regulator (CFTR) when expressed as separate polypeptides. The cross-linking of mutant [Delta]F508/NBD1(V510C)/TMD2(A1067C) restored by the correctors NBD1 and TMD2 indicated that the correctors promoted proper interactions between the two halves of CFTR.

Combination of high-resolution Fourier transform ion cyclotron resonance mass spectrometry and top-down fragmentation techniques were used to analyze the mechanistic details of hydrogen peroxide reduction by Escherichia coli bacterioferritin comigratory protein (BCP). The mutant BCP enzyme adopted a different and novel mechanistic pathway and reacted with peroxide to form a sulfenic acid on Cys-45 and is also a substrate for reduction by thioredoxin.

The changes in the transmembrane (TM) segments caused by human P-glycoprotein were examined. Catalytic carboxylate mutations were introduced into double cysteine mutants that exhibited ATP dependent cross linking and it was found that ATP alone cloud change disulfide cross-linking between TM segments.

Cysteine-scanning mutagenesis and oxidative cross-linking is used to test for changes in the packing of TM 11 during ATP hydrolysis. The results indicate that rearrangement of TM11 might contribute to the release of drug substrate during ATP hydrolysis.