Biomedical subjects

R V Talanian

Publications and source records attributed to R V Talanian.

6 recordsLinked to original sources

PubMed1995

Identification and characterization of ICH-2, a novel member of the interleukin-1 beta-converting enzyme family of cysteine proteases.

Interleukin-1 beta converting enzyme (ICE) is a cytoplasmic cysteine protease required for generating the bioactive form of the interleukin-1 beta cytokine from its inactive precursor. We report the identification of ICH-2, a novel human gene encoding a member of the ICE cysteine protease family, and characterization of its protein product. ICH-2 mRNA is widely expressed in human tissues in a pattern similar to, but distinct from, that of ICE. Overexpression of ICH-2 in insect cells induces apoptosis. Purified ICH-2 is functional as a protease in vitro. A comparison of the inhibitor profiles and substrate cleavage by ICH-2 and ICE shows that the enzymes share catalytic properties but may differ in substrate specificities, suggesting that the two enzymes have different functions in vivo.

Amino Acid Sequence↗

PubMed1992

Minimum length of a sequence-specific DNA binding peptide.

NMR experiments show that a stable complex can be formed between a 14-base-pair oligonucleotide and a disulfide-bonded dimer of a peptide containing 27 residues of the basic region of the yeast transcriptional activator GCN4; the complex is in slow exchange on the NMR time scale. In contrast, a nonspecific complex is in fast exchange on the NMR time scale. DNase I footprinting experiments show that dimers of peptides containing as few as 20 residues of GCN4 bind DNA with sequence specificity similar to that of the intact protein. Circular dichroism experiments suggest that specific binding involves only 15 residues, corresponding to residues 231-245 of GCN4, in an alpha-helical conformation. These results limit substantially the region of GCN4 involved in sequence-specific DNA contacts and provide a uniquely simple model for studying protein-DNA interactions in detail.

Amino Acid Sequence↗

PubMed1990

Sequence-specific DNA binding by a short peptide dimer.

A recently described class of DNA binding proteins is characterized by the "bZIP" motif, which consists of a basic region that contacts DNA and an adjacent "leucine zipper" that mediates protein dimerization. A peptide model for the basic region of the yeast transcriptional activator GCN4 has been developed in which the leucine zipper has been replaced by a disulfide bond. The 34-residue peptide dimer, but not the reduced monomer, binds DNA with nanomolar affinity at 4 degrees C. DNA binding is sequence-specific as judged by deoxyribonuclease I footprinting. Circular dichroism spectroscopy suggests that the peptide adopts a helical structure when bound to DNA. These results demonstrate directly that the GCN4 basic region is sufficient for sequence-specific DNA binding and suggest that a major function of the GCN4 leucine zipper is simply to mediate protein dimerization. Our approach provides a strategy for the design of short sequence-specific DNA binding peptides.

Amino Acid Sequence↗

PubMed1990

The roles of DNA polymerases alpha and delta in DNA replication.

The identities and precise roles of the DNA polymerase(s) involved in mammalian cell DNA replication are uncertain. Circumstantial evidence suggests that DNA polymerase alpha and at least one form of DNA polymerase delta, that which is stimulated by Proliferating Cell Nuclear Antigen, catalyze mammalian cell replicative DNA synthesis. Further, the in vitro properties of polymerases alpha and delta suggest a model for their coordinate action at the replication fork. The present paper summarizes the current status of DNA polymerases alpha and delta in DNA replication, and describes newly available approaches to the study of those enzymes.

Animals↗

PubMed1989

Carbonyldiphosphonate, a selective inhibitor of mammalian DNA polymerase delta.

Twenty-three pyrophosphate analogues were screened as inhibitors of proliferating cell nuclear antigen independent DNA polymerase delta (pol delta) derived from calf thymus. Carbonyldiphosphonate (COMDP), also known as alpha-oxomethylenediphosphonate, inhibited pol delta with a potency (Ki = 1.8 microM) 20 times greater than that displayed for DNA polymerase alpha (pol alpha) derived from the same tissue. Characterization of the mechanism of inhibition of pol delta indicated that COMDP competed with the dNTP specified by the template and was not competitive with the template-primer. In the case of pol alpha, COMDP did not compete with either the dNTP or the polynucleotide substrate. COMDP inhibited the 3'----5' exonuclease activity of pol delta weakly, displaying an IC50 greater than 1 mM.

Animals↗

PubMed1986

Naloxone's effects on intake of sequentially presented fluids.

Fluid-deprived rats were presented with one of three types of palatable solutions for 15 min, followed by access to either the same solution or one of the other types for 15 min. The solutions were 5.3% sucrose, 0.9% salt solution, and tap water. Naloxone reduced intake of all solutions, as compared to placebo, regardless of type of fluid or order of presentation. Rats receiving water followed by sucrose solution reduced their intake of water under naloxone, but did subsequently take a considerable amount of sucrose solution showing that they were capable of drinking more. These findings indicate that naloxone's effects closely track ordinary satiation-effects, merely enhancing satiation-like functions at each instance of opportunity to take fluids.

Animals↗