The group I intron of apocytochromebgene fromChlamydomonas smithiiencodes a site-specific endonuclease

✍ Scribed by Din-Pow Ma; Yueh-Tsu King; Kim Young; William S. Luckett

• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 370 KB
• Volume: 18
• Category: Article
• ISSN: 0167-4412
• DOI: 10.1007/bf00019218

✦ Synopsis

The mitochondrial DNA molecules of two interfertile algal species, Chlamydomonas smithii and C. reinhardtii, are co-linear except for a 1075 bp intron (the e-insert) that is present in the cob gene of C. smithii. The e-insert, a group I intron (Cs cob" 1) containing an open reading frame (ORF) which encodes a basic, hydrophilic protein of 237 amino acids, is unidirectionally transmitted to all diploid progeny during interspecific crosses. In this report, we show that the Cs cob" 1-encoded protein is a site-specific endonuclease (I-Csm I) which could mediate the intron transfer via the gene conversion mechanism. The Cs cob'l ORF was cloned into the vector pMALcrl and over-expressed as a hybrid protein fused to maltose-binding protein (MBP). This fusion protein exhibited an in vivo endonuclease activity which specifically cleaved the intron homing site within the intronless cob gene.