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Investigates the helix packing in the lactose permease of Escherichia coli. Distances between site-directed nitroxides and a lanthanide; Substrate protection of Cys148 in lactose permease; Specific direction of a methanethiosulfonate nitroxide spin-label to one of two Cys residues in a double-Cys mutant; Nitroxide-nitroxide interactions.

Deals with a study which examined the tertiary contacts between helices V and VII, VIII or X using a general cross-linking approach in the lactose permease. Experimental procedures; Results of the study; Discussion of the results.

Highlights a study which explored the N-terminal six transmembrane helices and the C-terminal transmembrane helices of the lactose permease, containing a single-Cys residue. Methodology; Cross-linking permease with paired Cys residues in helices IV and VII; Ligand-induced changes in cross-linking.

Studies the N-terminal six transmembrane helices (N6) and the C-terminal six transmembrane helices (C6) of lactose permease. Methods of the study; Relationships between helices I and VII; Effect of ligand in N6/C6 permease containing paired Cys residues; Results of the study.

Presents a study on the expressing of lactose permease. Expression in polypeptide fragments containing the N-terminal (N6) and C-terminal (C6) transmembrane domains; Views on the stability of the N6 and C6; Ability of C6 to catalyze lactose translocation.

Presents a study on the identification of the epitope for monoclonal antibody 4B1 which uncouples lactose and proton translocation in the lactose permease of Escherichia coli. Demonstration that 4B1 binds specifically to the periplasmic loop between helices VII and VIII; High specific interactions involved in the uncoupling effect of 4B1.

Describes the findings of a study on Escherichia coli, with mutants of a single Cys residue in place of Phe27, Pro28, Phe29, Phe30 or Pro31 at the periplasmic end of putative transmembrame helix I to find out the interaction of lactose permease with ligand by site-directed chemical modification or fluorescence spectroscopy.

Describes the use of site-directed fluorescence labeling to provide more direct evidence for the contention that cysteine (Cys) 148 is located in a binding site in the lactose (lac) permease of Escherichia coli. Plasmid construction; Purification of biotinated lac permease with single Cys residues; Protein determinations; Fluorescence quenching studies.