Topological requirements for recognition and cleavage of DNA by ribosome-inactivating proteins.
Ribosome-inactivating proteins (RIPs) were demonstrated to exhibit a unique enzymatic activity on cleaving supercoiled double-stranded DNA into the nicked or linear form. Although there is an interaction between supercoiled DNA and RIP, no sequence-specific recognition was involved. Instead, RIPs recognize supercoiled DNA by conformational specificity. Negatively supercoiled DNA is the preferential conformation in the action of RIPs. When double-stranded DNA occurs in the supercoiled form, even if with lower linking number, RIPs can still convert it into nicked or linear form. Terminal-labelling experiments indicated that radioactivity was incorporated into putative 5'-ends of nicked or linear DNA generated by RIPs. We conclude that RIPs act as a novel supercoil-dependent endonuclease when they cleavage supercoiled DNA. The impossibility that contaminating enzymes in the RIP preparations cleaved the supercoiled DNA is briefly discussed.
Ling
J
J
Shanghai Institute of Biochemistry, Academia Sinica, China.
Li
X
X
Wu
X
X
Liu
W
W
D020418:Algal Proteins; D002850:Chromatography, Gel; D018983:DNA Footprinting; D004278:DNA, Superhelical / Q000737:chemistry*; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D008970:Molecular Weight; D010940:Plant Proteins / Q000378:metabolism*; D011506:Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D012270:Ribosomes / Q000187:drug effects / Q000378:metabolism*
D020418:Algal Proteins; D004278:DNA, Superhelical; D005656:Fungal Proteins; D006023:Glycoproteins; D010940:Plant Proteins; D011506:Proteins; D054790:Ribosome Inactivating Proteins, Type 2; C061930:cinnamomin, Phytophthora cinnamomi; D004706:Endodeoxyribonucleases