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A Ciardiello

Publications and source records attributed to A Ciardiello.

18 recordsLinked to original sources
PubMed1993

Expression in mammalian cells, purification and characterization of recombinant human pancreatic ribonuclease.

A synthetic cDNA coding for human pancreatic RNase, equipped with a secretion signal sequence, was cloned and stably expressed in Chinese hamster ovary cells. The recombinant RNase, secreted into the culture medium, was purified and characterized. It was found to be indistinguishable, by structural and catalytic parameters, from the enzyme isolated from human pancreas. Furthermore, the glycosylated forms were separated from the non-glycosylated form. Up until now, human RNases have been isolated only in small amounts from autopic specimens. This has hindered the exploitation of a human RNase for the construction of immunotolerated immunotoxins. On the other hand, the availability of an effective system for the expression of a human RNase may render feasible the transfer, by protein engineering, of the interesting pharmacological actions of non-human RNase [1993 Trends Cell Biol. 3, 106-109] to an immunotolerated, human RNase.

Amino Acid Sequence↗
PubMed1988

Repair of isopeptide bonds by protein carboxyl O-methyltransferase: seminal ribonuclease as a model system.

Previous work has shown that in the peptide segment 62-76 of naturally deamidated alpha subunit of bovine seminal ribonuclease (BS-RNase) the alpha-carboxyl group of iso-Asp67 is selectively methylated by S-adenosylmethionine:protein carboxyl O-methyltransferase [Di Donato, A., Galletti, P., & D'Alessio, G. (1986) Biochemistry 25, 8361-8368]. In the present study this reaction has been characterized, by using the tryptic segment 62-76 of the protein chain (peptide alpha 16). The peptide is stoichiometrically methyl esterified with a Km of 6.17 microM and a Vmax of 19.56 nmol min-1 mg-1, and the product of demethylation has been identified as the cyclic succinimidyl derivative of iso-Asp67-Gly68. The cleavage of the succinimidyl ring yields two isomeric peptides containing an aspartyl residue (peptide alpha 17) and an isoaspartyl residue (peptide alpha 16). On the basis of these results conditions were defined in which repeated cycles of methylation-demethylation led to an effective conversion of peptide alpha 16 into peptide alpha 17, a process that can be interpreted as the repair of an altered isopeptide bond. When the methyl esterification reaction was studied on the native dimeric isoenzymes of seminal RNase and on catalytically active monomeric derivatives, including a stabilized alpha-type subunit, the results of these experiments showed that none of the protein forms were substrates for the methyltransferase. Only the unfolded alpha-type subunit was methylated to a stoichiometric extent. These results indicate that the repair of altered isopeptide bonds is chemically feasible in peptides but is hindered in the case of seminal RNase by its three-dimensional structure.

Amino Acid Sequence↗
PubMed1984

Distribution of radiolabelled azelaic cid in eye membranes and fluids of rabbits.

A direct cytotoxic effect of azelaic acid on melanocytes of human melanoma has been demonstrated. In view of a possible future therapeutic employment of this drug in the treatment of primary ocular melanoma, we investigated the route of choice of azelaic acid administration in rabbits. Our results evidenced a suden and direct blood absorption of topically (by retrobulbar injection) administered azelaic acid. This is in agreement with the high water solubility of azelaic acid sodium salt. These preliminary reports indicate that the elective route of azelaic administration in primitive eye melanoma is intravenously by continuous infusion.

Animals↗