XmnI

XmnI is a restriction enzyme of the Type II restriction endonuclease family used in molecular biology to cleave double-stranded DNA at specific sequences. It has been employed in cloning, DNA mapping, and various recombinant DNA applications due to its defined recognition site.

The enzyme recognizes the degenerate palindromic sequence 5'-GAANNNNTTC-3' (where N denotes any nucleotide) and its reverse complement. It binds this site and cleaves within the recognition sequence to generate double-stranded cuts. The 11-base-pair recognition site makes XmnI relatively infrequent in random DNA, enabling selective fragmentation in various cloning strategies.

XmnI is typically derived from Bacillus species and introduced into laboratory use in the latter part of the 20th century. In routine digestion, the enzyme is used in buffers containing Mg2+ and at temperatures around 37°C, with conditions such as buffer composition, DNA methylation status, and incubation time influencing activity. As with other restriction enzymes, non-ideal conditions can lead to star activity, producing off-target cuts.

Commercially available from multiple suppliers, XmnI is commonly used alongside other restriction enzymes to facilitate directional cloning, fragment analysis, and construction of recombinant plasmids. Its relatively long recognition sequence makes it a useful tool when precise, less frequent cutting is required in experimental design. References to XmnI can be found in standard enzyme databases and vendor manuals.