Presence of a protein specific of endocytobiosis (symbionin) in the weevil Sitophilus.

Chaperonins are ubiquitous proteins found in all prokaryotic and eukaryotic cells. They are overproduced in several parasitic bacteria and are implicated in at least 2 types of endocytobiosis: in amoebae and in aphids. This work puts in evidence that a protein named symbionin, which shows an immunological homology with the E. coli protein GroEL, is present in the symbiotic relationship of 3 species of Sitophilus (S. oryzae, S. granarius, and S. zeamais). This protein is neither found in the naturally asymbiotic specie S. linearis nor in the aposymbiotic strain of S. oryzae obtained in the laboratory. This symbionin is stored in a great quantity within endocytobiotes and its amino acid composition seems to corroborate its chaperonin resemblance rather than its possible function as one of the insect storage proteins already described in the literature.