510 G, H. BERGOLD 



B. mori and L. monacha polyhedron protein (Bergold and Scliramm, 1942). 

 In nonpurified polyhedron solutions two components with different mobilities 

 were found (Yamafuji et al., 1953a). Polyhedron protein seems not to migrate 

 on filter paper at pH 8.6 (Aizawa, 1955). Polyhedron protems spread readily 

 on water surfaces and can be loaded twice as much (55 dynes/cm.) as films 

 of casein or egg albumen. B. mori polyhedron protein has a maximum area 

 at pH 5 and those of P. dispar and L. monacha at pH 4. Between pH 1 and 7 

 the thickness of the films varies (Bergold and Brill, 1942). 



B. Chemical Composition of Inclusion Body Proteins 



Bolle (1893) first analyzed polyhedra and found that they consist of protein 

 and contain no lipids. A quantitative analysis of slightly impure B. mori 

 polyhedra revealed 14 % N, 0.79 % P, and 0.79 % S (Manunta, 1940). More 

 recent analyses of polyhedra and capsules and purified polyhedron and cap- 

 sule proteins are summarized in Table I. In comparing the results in 

 Table I, it should be realized that polyhedra and capsules consist of essenti- 

 ally two components: the polyhedron or capsule protein that constitutes 

 about 95 % of the total weight and the virus particles, about 5 % (Bergold, 

 1947, 1948). Therefore, analyses of polyhedra and capsules are, in effect, 

 analyses of polyhedron and capsule protein plus those of virus particles. 

 The N content of polyhedra, capsules, and purified protein preparations of 

 them, from different insect hosts, does not vary much and is about 14-15 %. 

 The P content of polyhedra varies with the preparation and is much smaller 

 in the purified polyhedron protein. The small amount of P (about 0.05 %) 

 that cannot be removed in spite of repeated precipitations and washings 

 may not even belong to the protein molecule and may be only adsorbed. 

 If it does belong, it can be calculated that each molecule of polyhedron 

 protein of P. dispar, L. monacha, and B. mori has about 4, 4, and 8 

 P atoms, respectively. Furthermore, not all split molecules — sixths and 

 eighteenths- — can possess one P atom. The difference of 50 to 60 % in 

 the P content between polyhedra and polyhedron protein is due to free 

 dialyzable phosphate, Hberated by the alkaline treatment (Desnuelle et al., 

 1943; Bergold, 1947). 



A search for metals has revealed only 0.005 % Fe in B. mori polyhedra and 

 polyhedron protein (Holoway and Bergold, 1953), 0.083 % Mg in polyhedra, 

 and no Mg in polyhedron protein (Holoway and Bergold, 1955). 



Desnuelle et al. (1943) and Desnuelle and Chang (1943) were the first to 

 determine the amino acid content of B. mori polyhedra and found (expressed 

 as % of protein N): cysteine and cystine, 0.4 %; alanine, 4.6 %; tyrosme, 

 5.2 %; histidine, 4.7 %; arginine, 12.1 %; phenylalanuie, 3.8 %; tryptophan, 

 3.00; ammonia, 6.4 %; and humin N, 3.8 %. An extensive investigation of the 



