The presence of copper-binding proteins produced in response
to added copper was examined in isolates of Laccaria laccata
(Scop. ex Fr.) Cooke and Paxillus involutus (Batsch ex Fr.)
Fr. taken from copper-contaminated and uncontaminated sites, and in a
single isolate of Scleroderma citrinum Pers. from a
contaminated site. Two isolates of Laccaria (GLac4 and
ELac1) grew better in 1·5 mM and 2·5
mM copper than a third (Lac3G) and were considered to be
more tolerant. Amongst five isolates of P. involutus, three
(WJPax2R, GPaxRSp2 and Pax4) were capable of growth in media
containing 4·0 mM copper and were regarded as
tolerant. All isolates of both Laccaria and
Paxillus were capable of some growth in 2·5
mM copper, but S. citrinum was much more
copper-sensitive and the concentration had to be reduced at least
10-fold before any growth occurred. Tolerance of isolates was not
related to whether they were taken from copper-contaminated or
uncontaminated sites. Copper-binding proteins were detected in
response to copper in the culture media in the two tolerant isolates
of Laccaria (GLac4 and ELac1) but not in the least tolerant
isolate. In Paxillus, similar proteins were found in two
tolerant isolates (GPaxRSp2 and Pax4) but not in
WJPax2R, which was also regarded as tolerant, nor in any of
the less tolerant isolates. Copper-binding proteins were not detected
in S. citrinum. The copper-binding protein purified from
the Laccaria isolate ELac1 appeared as a single band in
modified SDS–PAGE electrophoresis. Its molecular mass and
spectral characteristics were consistent with it being a
metallothionein.