DIFFERENT POSITIVELY CHARGED AMINO-ACIDS HAVE SIMILAR EFFECTS ON THE TOPOLOGY OF A POLYTOPIC TRANSMEMBRANE PROTEIN IN ESCHERICHIA-COLI
|Biochemistry & Molecular Biology; CYTOPLASMIC MEMBRANE; DOMAIN; LEADER PEPTIDASE; M13 PROCOAT; MEMBRANE-PROTEINS; MICROSOMAL MEMBRANE; PROCOAT PROTEIN; SECRETORY PROTEINS; SIGNAL PEPTIDE; TRANSLOCATION
|AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
|JOURNAL OF BIOLOGICAL CHEMISTRY
Integral membrane proteins from a wide variety of sources conform to a ``positive-inside rule,'' with many more positively charged amino acids in their cytoplasmic as compared to extracytoplasmic domains. A growing body of experimental work also points to positively charged residues in regions flanking the apolar transmembrane segments as being the main topological determinants. In this paper, we report a systematic comparison of the effects of positively (Arg, Lys, His) as well as negatively (Asp, Glu) charged residues on the membrane topology of a model Escherichia coli inner membrane protein. Our results show that positive charge is indeed the major factor determining the transmembrane topology, with Arg and Lys being of nearly equal efficiency. His, although normally a very weak topological determinant, can be potentiated by a lowering of the cytoplasmic pH. Asp and Glu affect the topology to similar extents and only when present in very high numbers.
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