A thiocyanate-forming protein generates multiple products upon allylglucosinolate breakdown in Thlaspi arvense

Jennifer-C Kuchernig, Anita Backenköhler, Maike Lübbecke, Meike Burow, Ute Wittstock
Phytochemistry 2011, 72 (14-15): 1699-709
Glucosinolates, amino acid-derived thioglycosides found in plants of the Brassicales order, are one of the best studied classes of plant secondary metabolites. Together with myrosinases and supplementary proteins known as specifier proteins, they form the glucosinolate-myrosinase system that upon tissue damage gives rise to a number of biologically active glucosinolate breakdown products such as isothiocyanates, epithionitriles and organic thiocyanates involved in plant defense. While isothiocyanates are products of the spontaneous rearrangement of the glucosinolate aglycones released by myrosinase, the formation of epithionitriles and organic thiocyanates depends on both myrosinases and specifier proteins. Hydrolysis product profiles of many glucosinolate-containing plant species indicate the presence of specifier proteins, but only few have been identified and characterized biochemically. Here, we report on cDNA cloning, heterologous expression and characterization of TaTFP, a thiocyanate-forming protein (TFP) from Thlaspi arvense L. (Brassicaceae), that is expressed in all plant organs and can be purified in active form after heterologous expression in Escherichia coli. As a special feature, this protein promotes the formation of allylthiocyanate as well as the corresponding epithionitrile upon myrosinase-catalyzed hydrolysis of allylglucosinolate, the major glucosinolate of T. arvense. All other glucosinolates tested are converted to their simple nitriles when hydrolyzed in the presence of TaTFP. Despite its ability to promote allylthiocyanate formation, TaTFP has a higher amino acid sequence similarity to known epithiospecifier proteins (ESPs) than to Lepidium sativum TFP. However, unlike Arabidopsis thaliana ESP, its activity in vitro is not strictly dependent on Fe²⁺ addition to the assay mixtures. The availability of TaTFP in purified form enables future studies to be aimed at elucidating the structural bases of specifier protein specificities and mechanisms. Furthermore, identification of TaTFP shows that product specificities of specifier proteins can not be predicted based on amino acid sequence similarity and raises interesting questions about specifier protein evolution.


You are not logged in. Sign Up or Log In to join the discussion.

Related Papers

Available on the App Store

Available on the Play Store
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"