TY - JOUR

T1 - Mechanism of postsegregational killing by the hok gene product of the parB system of plasmid R1 and its homology with the relF gene product of the E. coli relB operon

AU - Gerdes, K

AU - Bech, F W

AU - Jørgensen, Steen Troels

AU - Løbner-Olesen, A

AU - Rasmussen, P B

AU - Atlung, T

AU - Boe, L

AU - Karlstrom, O

AU - Molin, S

AU - von Meyenburg, K

PY - 1986/8

Y1 - 1986/8

N2 - The parB region of plasmid R1 encodes two genes, hok and sok, which are required for the plasmid-stabilizing activity exerted by parB. The hok gene encodes a potent cell-killing factor, and it is regulated by the sok gene product such that cells losing a parB-carrying plasmid during cell division are rapidly killed. Coinciding with death of the host cell, a characteristic change in morphology is observed. Here we show that the killing factor encoded by the hok gene is a membrane-associated polypeptide of 52 amino acids. A gene located in the Escherichia coli relB operon, designated relF, is shown to be homologous to the hok gene. The relF gene codes for a polypeptide of 51 amino acids, which is 40% homologous to the hok gene product. Induced overexpression of the hok and relF gene products results in the same phenomena: loss of cell membrane potential, arrest of respiration, death of the host cell and change in cell morphology. The parB region and the relB genes were cloned into unstably inherited oriC minichromosomes. Whereas the parB region also conferred a high degree of genetic stability to an oriC minichromosome, the relB operon (with relF) did not; therefore the latter does not appear to 'stabilize' its replicon (the chromosome). The function of the relF gene is not known.

AB - The parB region of plasmid R1 encodes two genes, hok and sok, which are required for the plasmid-stabilizing activity exerted by parB. The hok gene encodes a potent cell-killing factor, and it is regulated by the sok gene product such that cells losing a parB-carrying plasmid during cell division are rapidly killed. Coinciding with death of the host cell, a characteristic change in morphology is observed. Here we show that the killing factor encoded by the hok gene is a membrane-associated polypeptide of 52 amino acids. A gene located in the Escherichia coli relB operon, designated relF, is shown to be homologous to the hok gene. The relF gene codes for a polypeptide of 51 amino acids, which is 40% homologous to the hok gene product. Induced overexpression of the hok and relF gene products results in the same phenomena: loss of cell membrane potential, arrest of respiration, death of the host cell and change in cell morphology. The parB region and the relB genes were cloned into unstably inherited oriC minichromosomes. Whereas the parB region also conferred a high degree of genetic stability to an oriC minichromosome, the relB operon (with relF) did not; therefore the latter does not appear to 'stabilize' its replicon (the chromosome). The function of the relF gene is not known.

KW - Amino Acid Sequence

KW - Bacterial Proteins/genetics

KW - Base Sequence

KW - Escherichia coli/cytology

KW - Genes, Bacterial

KW - Genotype

KW - Kinetics

KW - Operon

KW - Plasmids

KW - R Factors

KW - Sequence Homology, Nucleic Acid

M3 - Journal article

C2 - 3019679

VL - 5

SP - 2023

EP - 2029

JO - E M B O Journal

JF - E M B O Journal

SN - 0261-4189

IS - 8

ER -