CHAPTER 12Mung-Bean Nuclease I (EC 3.1.30.1)
Andrew J. Sharp and Robert J. Slater
- Introduction
Mung-bean nuclease 1 was first purified by Sung and Laskowski (1)
in 1962 from mung-bean sprouts (Phaseolus aureus). It belongs to the
class of enzymes EC 3.1.30.1., which has a preference for single-
stranded nucleic acid substrates, lacks sugar specificity, and hydro-
lyzes single-stranded substrates to produce products with 5'-phosphoryl
and 3'-hydroxyl termini, ranging from mono- to, at least, heptanucleo-
tides. Although it shows a preference for single-stranded nucleic acids
over double-stranded of 30,000-fold (2), used in high concentrations
with extended incubation times, mung-bean nuclease 1 will completely
degrade double-stranded DNA (3-5). Mung-bean nuclease 1 is also
reported to show a separate 3'-to-monophosphatase activity (6) (see Sec-
tion 2.7.). Mung-bean nuclease 1 is a zinc metalloenzyme that requires
Zn 2+ and a reducing agent, such as cysteine, for both activity and stability.
Mung-bean nuclease 1 has been used in the removal of protruding
tails in double-stranded DNA, in the excising of cloned DNA frag-
ments inserted into vectors, and in other techniques we describe later
in this chapter. We also discuss some of the background enzyme data
for those wishing to understand the enzyme in more detail and for
those wishing to modify standard protocols to suit their own purposes.
Although it is not within the scope of this chapter to try to cover all of
the available data regarding specificity and mechanism of cleavage,
the information provided here should be adequate for most workers
seeking a general understanding.
From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology
Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ253