The replication terminator protein of E. coli is a DNA sequence-specific contra-helicase.
We have cloned the tus gene that encodes the replication terminator protein of Escherichia coli and have efficiently expressed its gene product. The overproducer strain has been used to purify the terminator (ter) protein in high yield to near homogeneity. The protein is a single 36 kd polypeptide. Using the ter protein and highly purified dnaB helicase, we show that the terminator protein is a DNA sequence-specific contra-helicase, i.e., the protein when bound to its recognition sequence (tau) strongly impedes the ATP-dependent unwinding of double-stranded DNA. This contra-helicase activity is polar, i.e., the impedance to unwinding takes place in only one orientation of the tau sequence. The results illuminate the mechanism of replication termination specifically at tau.
Khatri
G S
GS
Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710.
MacAllister
T
T
Sista
P R
PR
Bastia
D
D
D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D001483:Base Sequence; D004261:DNA Replication; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D015870:Gene Expression; D015723:Gene Library; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D015345:Oligonucleotide Probes; D010957:Plasmids; D015183:Restriction Mapping; D013728:Terminator Regions, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D015345:Oligonucleotide Probes; C061910:tus protein, Bacteria; C489236:tus protein, E coli