Chapter

Molecular Mechanisms of Metal Toxicity and Carcinogenesis

Volume 34 of the series Developments in Molecular and Cellular Biochemistry pp 97-106

Differential zinc and DNA binding by partial peptides of human protamine HP2

  • Wojciech BalAffiliated withFaculty of Chemistry, University of WroclawLaboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick
  • , Marcin DybaAffiliated withFaculty of Chemistry, University of Wroclaw
  • , Zbigniew SzewczukAffiliated withFaculty of Chemistry, University of Wroclaw
  • , Małgorzata Jeżowska-BojczukAffiliated withFaculty of Chemistry, University of Wroclaw
  • , Jan LukszoAffiliated withPeptide Analysis and Synthesis Unit, Research Technology Branch, National Institute of Allergy and Infectious Diseases
  • , Gayatri RamakrishnaAffiliated withLaboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick
  • , Kazimierz S. KasprzakAffiliated withLaboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick

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Abstract

The Zn(II) binding by partial peptides of human protamine IIP2: HP2]5;HP2:_25, HP220, HP237-07 and HP243_57was studied by circular dichroism (CD). Precipitation of a 20-mer DNA by these partial peptides and the effects of Zn(II) thereon were investigated using polyacrylamide gel electrophoresis (GE). The results of this study suggest that reduced HP2 (thiol groups intact) can bind Zn(II) at various parts of the molecule. In the absence of DNA, the primary Zn(II) binding site in reduced HP2 is located in the 37-47 sequence (involving Cys-37, His-39, His-43, and Cys-47), while in the presence of DNA, the strongest Zn(II) binding is provided by sequences 12-22 (by His-12, Cys-13, His-19, and His-22) and 43-57 (His-43, Cys-47, Cys-53, and His-57). In its oxidized form, HP2 can bind zinc through His residues of the 7-22 sequence. Zn(II) markedly enhances DNA binding by all partial peptides. These findings suggest that Zn(II) ions may be a regulatory factor for sperm chromatin condensation processes. (Mol Cell Biochem 222: 97-106, 2001)

Key words

protamine P2 protamine peptides DNA zinc protamine-zinc binding