DETECTION OF A PROTEIN-SPECIFIC TO HIGH-SALT DUNALIELLA CELLS

Dunaliella parva, a green unicellular alga, exists in mutually-interconvertible forms capable of growing in NaCl solutions from 0.2 M to at least 4 M. Interconversion between 0.5 M and 3.5 M NaCl takes 48 h in the upward and 1 1/2 h in the downward direction. Cultures are grown from single cells and must therefore be genetically identical. However, SDS-PAGE analysis of the insoluble cell fraction (largely membranes) has revealed that in cells grown in 3.5 M NaCl there is an extra polypeptide (Mr 140-160 kDa) that is not seen in cells grown in 0.5 M NaCl. The extra polypeptide has been found in all cultures growing in or above 2 M NaCl.