Similarity, in molecular structure and function, between the plant toxin purothionin and the mammalian pore-forming proteins.
Many proteins containing domains of a cysteine-rich repeated motif, such as epidermal growth factor (EGF), have been reported. Here we report strong similarity between the amino acid sequence of a plant toxin--i.e., purothionin and its homologues--and with those of a domain found in mammalian pore-forming cytoplasmic proteins: components of complement and perforin of cytotoxic T-lymphocytes or natural killer-like cytotoxic cells. These similar sequences were found to be identical to the so-called EGF-like cysteine-rich repeated motif itself. Electron-microscopic observations indicated that, like complement and perforin, purothionin forms pores in the cytoplasmic membrane of target cells, resulting in their death within a few hours. On the basis of these sequence comparisons and physiological functions, we propose a scheme for the evolution of proteins containing modules of the cysteine-rich repeat motif.
Oka
T
T
Department of Pathology, Kochi Medical School, Japan.
Murata
Y
Y
Nakanishi
T
T
Yoshizumi
H
H
Hayashida
H
H
Ohtsuki
Y
Y
Toyoshima
K
K
Hakura
A
A
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D023181:Antimicrobial Cationic Peptides; D004815:Epidermal Growth Factor / Q000737:chemistry; D006801:Humans; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000737:chemistry*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D015394:Molecular Structure; D054353:Perforin; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins; D016415:Sequence Alignment; D014118:Toxins, Biological / Q000737:chemistry* / Q000378:metabolism
D023181:Antimicrobial Cationic Peptides; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010940:Plant Proteins; D052899:Pore Forming Cytotoxic Proteins; D014118:Toxins, Biological; D054353:Perforin; D004815:Epidermal Growth Factor; C016085:purothionin