Identification of a virus intein and a possible variation in the protein-splicing reaction

• Published in: Current biology Vol. 8; no. 18; pp. R634 - R638
• Main Author: Pietrokovski, Shmuel
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 10.09.1998
• Subjects: Amino Acid Sequence; Animals; Genetic Variation; Insect Viruses - genetics; Insecta - virology; Molecular Sequence Data; Protein Splicing; Sequence Alignment; Sequence Homology, Amino Acid; Viral Proteins - chemistry; Viral Proteins - genetics
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/S0960-9822(07)00409-5

Organisms from all three kingdoms of life - eucarya, bacteria and archaea - contain inteins, but their distribution is sporadic. The presence of inteins in evolutionarily distant organisms and their variable appearance in related organisms is generally explained by horizontal transfer. The extent of intein horizontal transfer has health implications: Mycobacterium tuberculosis, Mycobacterium leprae and Candida tropicalis are major human pathogens that contain inteins. Here, I describe the first identified insect virus intein. On the basis of the sequence relation of the viral intein and its protein host to other proteins, I propose viruses as vehicles of intein dispersion. A new type of residue in the intein's carboxy-terminal end suggests a variation of the protein-splicing mechanism. The ribonucleotide reductase (RNR) large subunit of the Chilo iridescent virus (CIV) contains an intein. CIV is an insect-infecting iridovirus; members of this double-stranded DNA virus family are known to infect invertebrates, amphibia and fish. All the expected protein-splicing motifs are found in the intein together with the typical dodecapeptide LAGLIDADG homing-endonuclease domain. The glutamine at the carboxy-terminal intein end, where only asparagine has been observed before, indicates a variation on the previously described protein-splicing mechanism.