In my previous blog, I briefly mentioned the hammerhead ribozyme. This article talks about them in more depth. Hammerhead ribozymes are tiny, self-cleaving RNAs that boost strand scission by internal phosphoester transfer. They have two types; type I and type II. They also have two major properties which are cleavage site specificity and catalytic activity.
To identify numerous additional representatives of this ribozyme class (including the first representatives in fungi and archaea), comparative sequence analysis was used. The first natural samples of “type II” hammerheads have been uncovered. These results show that this altered form occurs in bacteria as frequently as type I and III architectures. A commonly occurring pseudoknot that forms a tertiary interaction that is very important for high-speed ribozyme activity has also been discovered. Genomic factors of many hammerhead ribozymes can tell what biological functions they perform that are different from their known role in generating unit-length RNA transcripts of multimeric viroid and satellite virus genomes. In rare occurrences, nucleotide variation occurs at places within the catalytic core that are otherwise strictly conserved. Thus suggesting that core mutations are occasionally tolerated or even preferred.
To identify numerous additional representatives of this ribozyme class (including the first representatives in fungi and archaea), comparative sequence analysis was used. The first natural samples of “type II” hammerheads have been uncovered. These results show that this altered form occurs in bacteria as frequently as type I and III architectures. A commonly occurring pseudoknot that forms a tertiary interaction that is very important for high-speed ribozyme activity has also been discovered. Genomic factors of many hammerhead ribozymes can tell what biological functions they perform that are different from their known role in generating unit-length RNA transcripts of multimeric viroid and satellite virus genomes. In rare occurrences, nucleotide variation occurs at places within the catalytic core that are otherwise strictly conserved. Thus suggesting that core mutations are occasionally tolerated or even preferred.
Hammerhead Ribozymes have three helical stem regions and unpaired loops at the ends of two helices. Helices radiate out from central unpaired core of nucleotides. The cleavage site is next to a small, unpaired "U-turn" loop.
This picture shows the secondary and tertiary structure of a hammerhead ribozyme.
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