Biomaterial Database

lac permease of Escherichia coli: histidine-205 and histidine-322 play different roles in lactose/H+ symport. 1986

I B Püttner, and H K Sarkar, and M S Poonian, and H R Kaback

The lac permease of Escherichia coli was modified by site-directed mutagenesis such that His-205 or His-322 is replaced with either Asn or Gln. Permease with Asn or Gln in place of His-205 exhibits normal activity, while permease with Asn or Gln in place of His-322 exhibits no activity. The results are consistent with the interpretation that His-205 and His-322 play different roles in lactose/H+ symport, the former involving hydrogen bonding of the imidazole nitrogens and the latter requiring positive charge in the imidazole ring. In addition, it is demonstrated that permease with Arg in place of His-322 does not catalyze efflux, exchange, or counterflow. The observations, in conjunction with those in the accompanying paper [Carrasco, N., Antes, L. M., Poonian, M. S., & Kaback, H. R. (1986) Biochemistry (following paper in this issue)], suggest that His-322 plays an important role in H+ translocation, possibly as a component of a charge-relay system with Glu-325, a neighboring residue in helix 10.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D007785	Lactose	A disaccharide of GLUCOSE and GALACTOSE in human and cow milk. It is used in pharmacy for tablets, in medicine as a nutrient, and in industry.	Anhydrous Lactose,Lactose, Anhydrous
D009004	Monosaccharide Transport Proteins	A large group of membrane transport proteins that shuttle MONOSACCHARIDES across CELL MEMBRANES.	Hexose Transport Proteins,Band 4.5 Preactin,Erythrocyte Band 4.5 Protein,Glucose Transport-Inducing Protein,Hexose Transporter,4.5 Preactin, Band,Glucose Transport Inducing Protein,Preactin, Band 4.5,Proteins, Monosaccharide Transport,Transport Proteins, Hexose,Transport Proteins, Monosaccharide,Transport-Inducing Protein, Glucose
D009154	Mutation	Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.	Mutations
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D006639	Histidine	An essential amino acid that is required for the production of HISTAMINE.	Histidine, L-isomer,L-Histidine,Histidine, L isomer,L-isomer Histidine
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA
D026901	Membrane Transport Proteins	Membrane proteins whose primary function is to facilitate the transport of molecules across a biological membrane. Included in this broad category are proteins involved in active transport (BIOLOGICAL TRANSPORT, ACTIVE), facilitated transport and ION CHANNELS.	Biological Pump,Membrane Transport Protein,Membrane Transporter,Membrane Transporters,Metabolic Pump,Permease,Biological Pumps,Metabolic Pumps,Permeases,Pump, Biologic,Pump, Biological,Pump, Metabolic,Pumps, Biological,Pumps, Metabolic,Biologic Pump,Protein, Membrane Transport,Transport Protein, Membrane,Transport Proteins, Membrane,Transporter, Membrane,Transporters, Membrane
D027981	Symporters	Membrane transporters that co-transport two or more dissimilar molecules in the same direction across a membrane. Usually the transport of one ion or molecule is against its electrochemical gradient and is "powered" by the movement of another ion or molecule with its electrochemical gradient.	Co-Transporter,Co-Transporters,Symporter,Co Transporter,Co Transporters