Transport of metal-binding peptides by HMT1, a fission yeast ABC-type vacuolar membrane protein.

The Schizosaccharomyces pombe hmt1 gene encodes an ABC (ATP-binding cassette)-type protein essential for Cd2+ tolerance. Immunoblot analysis of subcellular fractions indicates that the native HMT1 polypeptide is associated with the vacuolar membrane. Vacuolar membrane vesicles were purified from strains that hyperproduce, or are deficient in, the HMT1 protein.

DNA polymerase I modulates inducible stable DNA replication in Escherichia coli.

Mutants of Escherichia coli lacking RNase HI activity and cells induced for the SOS response express modes of DNA replication independent of protein synthesis, called constitutive and induced stable DNA replication, respectively. We report here that mutants deleted for the polA gene express induced stable DNA replication at approximately 25-fold the rate of wild-type cells, whereas constitutive stable DNA replication is not enhanced.

Selective immunoneutralization of the multiple activities of Escherichia coli DNA polymerase I supports the model for separate active sites and indicates a complex 5' to 3' exonuclease.

DNA polymerase I (pol I) from Escherichia coli has three well-defined activities: DNA polymerase, 3'-5' exonuclease, and 5'-3' exonuclease. We have raised monoclonal antibodies to pol I which selectively neutralize each of these three activities, thus supporting the model of separate active sites for each activity, heretofore exclusively demonstrated with proteolytic fragments of pol I. Antibodies from each class could bind pol I in the presence of antibodies of another class, indicating the existence of significant spatial separation between each of the three sites.