A five-residue sequence near the carboxyl terminus of the polytopic membrane protein lac permease is required for stability within the membrane

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.86.11.3992· OSTI ID:5161198

Roepe, P D; Zbar, R I.S.; Sarkar, H K; Kaback, H R ^[1]

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1. Roche Research Center, Nutley, NJ (USA)

The lac permease (lacY gene product) of Escherichia coli contains 417 amino acid residues and is predicted to have a short hydrophilic amino terminus on the inner surface of the cytoplasmic membrane, multiple transmembrane hydrophobic segments in {alpha}-helical conformation, and a 17-amino acid residue hydrophilic carboxyl-terminal tail on the inner surface of the membrane. To assess the importance of the carboxyl terminus, the properties of several truncation mutants were studied. Permease truncated at position 407 or 401 retains full activity, and a normal complement of molecules is present in the membrane. In marked contrast, when truncations are made at residues 396, 389, 372, or 346, the permease is no longer found in the membrane. Remarkably, however, when each of the mutated lacY genes is expressed at a high rate by means of the T7 RNA polymerase system all of the truncated permeases are present in the membrane, as indicated by ({sup 35}S)methionine incorporation studies. Finally, pulse-chase experiments indicate that wild-type permease or permease truncated at residue 401 is stable, whereas permease truncated at or prior to residue 396 is degraded at a significant rate. The results are consistent with the notion that residues 396-401 in putative helix XII are important for protection against proteolytic degradation and suggest that this region of the permease may be necessary for proper folding.

• OSTI ID: 5161198
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 86:11; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBON 14 COMPOUNDS
MEMBRANE TRANSPORT
CELL MEMBRANES
ENZYME ACTIVITY
MEMBRANE PROTEINS
MUTAGENESIS
AMINO ACID SEQUENCE
HYDROLASES
LACTOSE
MEMBRANES
METHIONINE
PROTEINS
SULFUR 35
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBOHYDRATES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
DAYS LIVING RADIOISOTOPES
DISACCHARIDES
DRUGS
ENZYMES
EVEN-ODD NUCLEI
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPOTROPIC FACTORS
MOLECULAR STRUCTURE
NUCLEI
OLIGOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
RADIOISOTOPES
SACCHARIDES
SULFUR ISOTOPES
550201* - Biochemistry- Tracer Techniques