Both N- and C-terminal regions are essential for cinnamomin A-chain to deadenylate ribosomal RNA and supercoiled double-stranded DNA.
Cinnamomin is a type II ribosome-inactivating protein and its A-chain exhibits RNA N-glycosidase activity to remove an adenine in the conserved sarcin/ricin loop of the largest RNA in ribosome, arresting protein synthesis at the elongation step. In this report, deadenylation of both rRNA and supercoiled DNA by native and recombinant cinnamomin A-chain expressed in Escherichia coli was demonstrated. However, the mutants of cinnamomin A-chain devoid of N-terminal 52 or/and C-terminal 51 amino acid residues lost both the activity of RNA N-glycosidase and the ability to release adenines from supercoiled DNA. Additionally, supercoiled DNA could not be cleaved into nicked and linear forms by these mutants. These results indicate that both N- and C-terminal regions are essential for the cinnamomin A-chain to deadenylate rRNA and supercoiled DNA. It was suggested that phosphodiester bonds in the extensively deadenylated region of supercoiled DNA would become fragile and liable to be broken spontaneously owing to the existence of tension in the supercoiled DNA.
He
Wen-Jun
WJ
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, People's Republic of China.
Liu
Wang-Yi
WY
D000225:Adenine / Q000378:metabolism; D020418:Algal Proteins; D000595:Amino Acid Sequence; D001483:Base Sequence; D004278:DNA, Superhelical / Q000737:chemistry / Q000378:metabolism*; D009699:N-Glycosyl Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D054788:Ribosome Inactivating Proteins; D054790:Ribosome Inactivating Proteins, Type 2; D017384:Sequence Deletion
D020418:Algal Proteins; D004278:DNA, Superhelical; D011506:Proteins; D012335:RNA, Ribosomal; D011994:Recombinant Proteins; D054790:Ribosome Inactivating Proteins, Type 2; C061930:cinnamomin, Phytophthora cinnamomi; D009699:N-Glycosyl Hydrolases; D054788:Ribosome Inactivating Proteins; D000225:Adenine