synthesis with the proto-ribosomes must have arisen in exchange with the
heterotrophic pre-cell formation of primary proteinoids”.
Of certain interest are the studies of Ch. Ivanov and O. Ivanov (1973—
93) on the possibility of proteolytic shortening of the long-chain ancient
proteins (built from a smaller number of amino acids bound on the basis of
preference towards structurally and functionally similar amino acid, as a result
of which short-chain proteins or fragments are obtained that are able to
combine among themselves until reaching functional sufficiency) to have
played an important role at the earliest stages of protein evolution. Thus, the
tendency in the molecular evolution of proteins from the ordinary amino acids
(gly, ala, pro, arg, val, leu, asp, glu, ser, thr) to the specialized ones (asn, gln,
lys, his, ile, met, cys, phe, tyr, trp) was revealed (Ivanov, 1989 a, 1993).
Recently, the problem and respectively the discussions on prions has
provoked considerable interest. The term was suggested by S. Prusiner
(1982) for designating the transmitter of the scrapie disease (proteinaceous
infectious particles) that has inflicted heavy damages on sheep and goat
flocks around the world and Scotland in particular. Based on studies of his
as well as on data of other researchers, the author implies two possible
models of the agent’s structure: a minute nucleic acid thickly wrapped in a
protein capsule, or a protein free of nucleic acids i.e. an infectious protein.
In his view this protein acts as an inductor or a matrix for its own synthesis.
It is now accepted that prions or the infectious proteins are the cause of
certain typical diseases such as Creutzfeldt—Jakob’s and the Gerstmann—
Sträussler—Scheinker’s syndromes in man and some encephalopathies in
animals characterized with a high lethality rate. Sometimes they develop very
rapidly and death comes within several months.
In a disputable article Kordyum (1990) after analyzing the data from
investigations on prions motivates his proposal, that as a supplement to
the widely-known type the genetic coding in the form of primary sequence
of nucleic acids there exists another form of biological information transfer
which is the spatial structure of proteins capable of self-reproduction (Fig.
1–7). “It is found — states the author — that pure protein molecules
without the presence of nucleic acids are capable in some way to ensure
in the cell their own multiplication, accumulation and realization of the
pathological process and have the capacity when invading a healthy
organism to carry out this cycle from the beginning”. According to his data
there are six typically prion-induced disorders known by now, but he
admits that their diversity might be greater. The presence of prions in
yeasts and their wide spread in nature is supported by other authors
(Vogel, 1996; Patino et al., 1996).