Direct characterisation by electrospray ionisation mass spectroscopy of mercuro-polypeptide complexes after deprotection of acetamidomethyl groups from protected cysteine residues of synthetic polypeptides.
In this paper, we describe a rapid procedure to characterise the products generated in the presence of mercuric salts following removal of the acetamidomethyl (Acm)-protecting group from cysteine residues of synthetic polypeptides prepared by solid-phase peptide synthesis (SPPS) methods. In particular, electrospray ionisation mass spectrometry (ESI-MS) procedures have been employed to characterise the mercuro-polypeptide products related to the ribosomal L36 protein isolated from the bacterium Thermus thermophilus. The results demonstrate that very stable mercuro-polypeptide complexes can form under standard conditions of deprotection involving Hg(2+) salts in the presence of a reductant such as beta-mercaptoethanol. Metal ion exchange effects involving other divalent metal ions, such as Co(2+) or Zn(2+), can also be monitored by similar procedures, thus permitting the relative affinity and selectivity for metal ion-polypeptide interactions to be qualitatively assessed. Since the Thermus thermophilus ribosomal L36 protein contains a putative zinc finger binding CCCH motif, these procedures enable the formation of metal-ion complexes of synthetic polypeptides related to this structural motif to be directly examined.
Boysen
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RI
Centre for Bioprocess Technology, Department of Biochemistry and Molecular Biology, Monash University, Clayton, 3168, Victoria, Australia.
Hearn
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MT
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry*; D008969:Molecular Sequence Data; D009941:Organomercury Compounds / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D012269:Ribosomal Proteins / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D016963:Thermus thermophilus / Q000737:chemistry; D016335:Zinc Fingers
D001426:Bacterial Proteins; D009941:Organomercury Compounds; D010455:Peptides; D012269:Ribosomal Proteins; D003545:Cysteine