Substitution of glutamine-60 with glutamic acid causes the lac permease of Escherichia coli to become temperature sensitive.
The lac Y gene of Escherichia coli was modified by oligonucleotide-directed, site-specific mutagenesis so that Gln-60 is replaced with Glu. Although the replacement introduces a negative charge into a putative hydrophobic, transmembrane alpha-helical segment of the lac permease, lactose/H+ symport is unimpaired. However, the modified permease is more susceptible to heat inactivation. That is, upon incubation at 45 degrees C, Glu-60 permease loses activity with a t1/2 of 20 min relative to a t1/2 of 50 min with wild-type permease.
Sarkar
H K
HK
Viitanen
P V
PV
Poonian
M S
MS
Kaback
H R
HR
D001483:Base Sequence; D004262:DNA Restriction Enzymes; D004274:DNA, Recombinant / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D005796:Genes; D005798:Genes, Bacterial; D005971:Glutamates; D018698:Glutamic Acid; D005973:Glutamine; D007700:Kinetics; D007785:Lactose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D013696:Temperature
D004274:DNA, Recombinant; D029968:Escherichia coli Proteins; D005971:Glutamates; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D005973:Glutamine; D018698:Glutamic Acid; C021499:lactose permease; D004262:DNA Restriction Enzymes; D007785:Lactose