Methods in Molecular Biology • 16 Enzymes of Molecular Biology

CHAPTER 11

The BAI, 31 Nucleases (EC 3.131)

Horace B. Gray, Jr. and Tao Lu

1. Introduction
   1.1. Source
   The extracellular nucleases commonly called the BAL 31 nuclease
   take their name from the designation given the marine bacterium pro-
   ducing them, which was originally classified as Pseudomonas BAL 31
   (1) and reclassified as belonging to the small genus Alteromonas (2)
   with the species named espejiana after its discoverer, a Chilean micro-
   biologist. The nuclease activities were originally found as contami-
   nants in preparations of bacteriophage PM2 grown on this organism,
   but were shown (3,4) to be bacterial products. Only 10-20% of the
   nuclease activity is found in the periplasm (5). The American Type
   Culture Collection strain of Alteromonas espejiana (ATCC 29659)
   produces BAL 31 nuclease as proficiently as the strain originally
   obtained from its discoverer.

1.2. Some Physical Features
Two kinetically and molecularly distinct forms of the nuclease con-
stitute the bulk of the activity in culture supernatants and are the only
ones that have been partially characterized (6). The smaller of these
single-subunit enzymes, the "slow" (S) form (mol mass 85,000 Da),
is derived by proteolysis, mediated by an Alteromonas-produced pro-
tease, of the "fast" (F) form (mol mass 109,000 Da), which in turn
derives from an even larger precursor (7). Conversion ofF nuclease to
a species indistinguishable in molecular size and catalytic properties
from the S enzyme can be done by proteolysis in vitro (7).

From: Methods in Molecular Biology, VoL 16: Enzymes of Molecular Biology

Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

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