T4 RNA Ligase 2, truncated KQ (T4 Rnl2tr R55K, K227Q) specifically ligates the preadenylated 5´ end of DNA or RNA to the 3´ OH end of RNA.

The enzyme does not use ATP for ligation but requires pre-adenylated linkers. T4 Rnl2tr R55K, K227Q is a double-point mutant of T4 RNA Ligase 2, truncated. Mutation of K227 in T4 RNA Ligase 2 reduces enzyme lysyl adenylation. K227Q reduces the formation of undesired ligation products (concatemers and circles) by T4 Rnl2tr, by reducing the trace activity of T4 Rnl2tr in transfer of adenylyl groups from linkers to the 5´-phosphates of input RNAs. Mutation of R55K in T4 Rnl2tr K227Q increases the ligation activity of the enzyme to levels similar to T4 Rnl2tr. The exclusion of ATP, use of pre-adenylated linkers, and the reduced enzyme lysyl adenylation activity provide the lowest possible background in ligation reactions. This enzyme has been used for optimized linker ligation for high-throughput sequencing library construction of small RNA.