Fletcher (L) and biochemistry student Heather Young at
his lab in the Ocean Sciences Centre.
By Deborah Inkpen
Dr. Garth Fletcher, professor emeritus at the Ocean
Sciences Centre, has been working with his colleague, Dr.
Peter Davies, Queen’s University, for over 30 years
on antifreeze proteins in fish.
A number of marine fish produce antifreeze proteins to protect
themselves from freezing in a sub-zero, ice-laden marine environment.
“The research we are carrying out focuses on these antifreeze
proteins, their physiological regulation, mechanisms of action,
diversity, evolution and potential economic value in the field
of biotechnology,” said Dr. Fletcher.
Drs. Fletcher and Davies’ collaboration with graduate
student Christopher Marshall, Queen’s University on
the winter flounder was recently published in Nature magazine.
“The winter flounder can survive in polar oceans at
temperatures as low as minus 1.9 degrees Celsius, the freezing
point of seawater,” said Dr. Fletcher.
How the flounder does this is a mystery.
“The fish only seemed to have enough ‘antifreeze’
protection to cater for temperatures down to minus 1.5 degrees
The solution to the mystery is a newly identified antifreeze
protein present in the fish's blood that has a remarkable
“It was there all along, but we missed it and it took
30 years to find it.”
that live in polar oceans survive at low temperatures by virtue
of antifreeze plasma proteins (AFPs) that bind to ice crystals
and prevent them from inflicting cellular damage. The winter
flounder (Pleuronectes americanus) has a much-studied
AFP known as type I, but it is this new protein that enables
the fish to withstand freezing sea water. This additional
AFP is hyperactive, offering a level of protection equivalent
to that of an insect AFP.
“The new protein may be the product of a flounder gene
of previously unknown function, called 5a,” said Dr.
Fletcher. “It irreversibly loses all activity at room
temperature and at low pH – conditions formerly used
in purifying antifreeze proteins – which may explain
why it remained undetected for 30 years.”