Accumulation and protection activity of protease-resistant heat-stable proteins in Haematococcus pluvialis during high light and nitrogen starvation

Under stress conditions of high light and nitrogen starvation the green motile cells of the unicellular green alga Haematococcus pluvialis are known to cease growing and transform into inert red cysts, in which the secondary carotenoid astaxanthin accumulates. A study was therefore made on other effects of such conditions. A number of protease-resistant, heat-stable proteins with apparent molecular masses of 38 kDa, 50 kDa, 62 kDa and 63 kDa accumulated. This protein fraction was effective in the protection of horseradish peroxidase from inactivation, suggesting a role for these proteins in H. pluvialis subjected to a stress event.