SmaI
| Type-2 restriction enzyme SmaI | ||
|---|---|---|
| other names |
Endonuclease SmaI, Type II restriction enzyme SmaI |
|
| Mass / length primary structure | 247 amino acids , 28,782 Da | |
| Secondary to quaternary structure | Homodimer | |
| Identifier | ||
| Gene name (s) | SmaI (Rebase) | |
| External IDs | ||
| Enzyme classification | ||
| EC, category | 3.1.21.4 , restriction enzyme | |
| Response type | hydrolysis | |
| Substrate | DNA | |
| Products | Double stranded DNA fragments with terminal 5 'phosphate groups | |
| Occurrence | ||
| Parent taxon | Serratia marcescens | |
SmaI is a restriction enzyme from the bacterium Serratia marcescens .
properties
SmaI is an endonuclease (type II, subtype P) that cuts DNA at a palindromic DNA recognition sequence . The cut of the double-stranded DNA by SmaI results in a blunt end (end without overhang) and a phosphate group at each of the 5 'ends of the double-stranded DNA products. SmaI is not inhibited by either DAM or DCM methylation, but by CpG methylation. Among the CpG methylation- sensitive restriction enzymes SmaI (recognition sequence CCCGGG), HpaII (CCGG), HhaI (GCGC), AciI (GCGC), BstUI (CGCG) and HpyCH4IV (ACGT), SmaI has the longest recognition sequence with six base pairs. At 37 ° C the enzyme activity is about 50% of the enzyme activity at 25 ° C. In suboptimal buffer conditions , the affinity of SmaI for the recognition sequence decreases and the DNA is cut unspecifically ( star activity ). After restriction of DNA in vitro , SmaI can be denatured and thus inactivated by heating to 65 ° C for 20 minutes . Most of the time, SmaI is produced as a recombinant protein in E.coli . The restriction enzymes XmaI and Cfr9I are neoschizomers of SmaI.
| Recognition sequence | Restriction cut |
|---|---|
5'-CCCGGG-3' 3'-GGGCCC-5' |
5'-CCC GGG-3' 3'-GGG CCC-5' |
Applications
SmaI is used for restriction digests in the context of cloning or restriction analyzes. Because of the inhibition by methylated CpG motifs, SmaI is used to study DNA methylation .
Individual evidence
- ↑ a b Jeffrey Craig: Epigenetics. Horizon Scientific Press, 2011, ISBN 978-1-904-45588-2 , p. 349.
- ↑ MA Argudín, MR Rodicio, B. Guerra: The emerging methicillin-resistant Staphylococcus aureus ST398 clone can Easily be typed using the Cfr9I Smal neoschizomer. In: Letters in applied microbiology. Volume 50, number 1, January 2010, pp. 127-130, doi : 10.1111 / j.1472-765X.2009.02742.x , PMID 19843206 .