Single amino acid substitutions affecting the specificity of the fungal ribotoxin mitogillin

FEBS Letters

Kao, Richard¹  Davies, Julian¹ 

[1] Department of Microbiology and Immunology, The University of British Columbia, 6174 University Blvd., Vancouver, B.C. V6T 1Z3, Canada

关键词: Mitogillin;    Restrictocin;    Ribotoxin;    Specificity;    Targeted toxin;    α-Sarcin/ricin loop;   

DOI  :  10.1016/S0014-5793(99)01753-6

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Mitogillin and related fungal ribotoxins are small basic ribonucleolytic proteins that inhibit protein synthesis by specifically hydrolyzing a single phosphodiester bond in the universally conserved α-sarcin/ricin loop (SRL) of large subunit ribosomal RNAs. It was previously shown that mitogillin is a natural derivative of a T1/U2-like ribonuclease with inserted domains that are involved in target selection and specificity. Site-directed mutagenesis was used to substitute single amino acids in the previously identified functional domains Ala1–Tyr24 (B1-L1-B2 domain) and Lys106–Lys113 (L4 region). Examination of the activities of the mutants in the digestion of polyinosinic acid (a ribonuclease substrate) and specific cleavage of the SRL shows that Asn7Ala and Lys111Gln substitutions lead to altered ribonuclease activity and diminished substrate specificity consistent with the proposed functions of these domains.

【 授权许可】

Unknown