title: Covalent sequestration of melphalan by metallothionein and selective alkylation of cysteines.
abstract: Rabbit liver metallothionein-2 is shown to form covalent bonds with the anticancer agent melphalan, in support of the hypothesis that covalent sequestration by metallothionein constitutes one mechanism for the cross-resistance acquired by cancer patients to therapeutic alkylating agents. Among 20 cysteines in the 2-domain protein, 89% of the first alkylation reaction occurs with 2 that cochelate a zinc cation in the carboxy domain. Computer-supported docking studies indicate a favorable binding site for melphalan near these cysteine sulfhydryl groups. Although folded metallothionein-2 is resistant to trypsin cleavage, alkylation by 1 mol of melphalan allows cleavage by trypsin between the two globular domains.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland Baltimore County 21228.
authors.forename: X
authors.initials: X
authors.lastname: Yu
authors.forename: Z
authors.initials: Z
authors.lastname: Wu
authors.forename: C
authors.initials: C
authors.lastname: Fenselau
mesh_terms: D000478:Alkylation; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D003545:Cysteine / Q000737:chemistry; D004351:Drug Resistance; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism; D008558:Melphalan / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D008668:Metallothionein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D010446:Peptide Fragments; D008668:Metallothionein; D003545:Cysteine; D008558:Melphalan