306
JOHN RUNNSTRÖM
and Β. Any substance incorporated later must insert itself into the given
framework. This consists of the compartmented filaments of the lamellae.
The sharp turning point in Markman's curve (Fig. 33) may be interpreted as the effect of the onset of a secretion of a factor from the egg.
This was called the "membrane toughening factor" (MTF) by Motomura
(1950). E. Hultin et al. (1952) gave reasons for believing that this factor
is identical with the jelly precipitating factor (the "antifertilizin" of
Fr. Lillie, 1919). Motomura (1957) has isolated the membrane-toughening factor, which seems to be a basic protein; he proposes the designation
"colleterin." Like the basic protein lysozyme, the effect of which was
described in Section ΙΠ,Β, the MTF may react with different acid components of the vitelline membrane and the lamellae and in this way bring
about the solidifying linkages.
The situation in the solidified membrane may, however, be a more
complicated one. It has been recorded above that even the connections
between the filaments of the lamellae are sensitive to reduced glutathione.
The delayed lamellae had a more open structure when ribonucleasetreated eggs underwent a subsequent treatment with reduced glutathione.
It may be remembered also that both thioglycolic acid and cysteine
prevent the hardening of the elevating fertilization membrane (Runnström et al, 1943). Monroy (1949) and Monroy and Runnström (1948)
showed that the solidified fertilization membrane of Psammechinus
eggs
gets softer upon treatment with thioglycolic acid at pH 6.0 and 7.5. This
indicates a reduction of SH groups. Furthermore, after pretreatment with
thioglycolic acid, the fertilization membrane became rather sensitive to
chymotrypsin (about 10~
4 Anson units), whereas the sensitivity to trypsin
of nearly the same titer was rather low. This would indicate that tyrosine
groups would be available in the fertilization membrane and that
tyrosine plays a decisive role in the stability of the fertilization membrane. Ths may depend on the reactivity of the phenol groups present
in tyrosine. It is peculiar that trypsin does not have a stronger effect
in view of the fact that the "toughening factor" seems to be a basic
protein and thus should contain arginine and lysine. This research should
be repeated with several different species as material.
It follows from the curve of Fig. 33 that Ca
2+ is also necessary for the
solidification of the membrane (see also Hobson, 1927). The Ca
2+ may be
able to bind together acid groups that have not reacted with the basic
groups of MTF.
The delayed lamellae are converted into rods or plates at the same time
as the toughening of the fertilization membrane occurs. There is also
striking simultaneity in the conversion of the delayed lamellae even when
their number is rather large (Runnström, 1948). This points definitely
JOHN RUNNSTRÖM
and Β. Any substance incorporated later must insert itself into the given
framework. This consists of the compartmented filaments of the lamellae.
The sharp turning point in Markman's curve (Fig. 33) may be interpreted as the effect of the onset of a secretion of a factor from the egg.
This was called the "membrane toughening factor" (MTF) by Motomura
(1950). E. Hultin et al. (1952) gave reasons for believing that this factor
is identical with the jelly precipitating factor (the "antifertilizin" of
Fr. Lillie, 1919). Motomura (1957) has isolated the membrane-toughening factor, which seems to be a basic protein; he proposes the designation
"colleterin." Like the basic protein lysozyme, the effect of which was
described in Section ΙΠ,Β, the MTF may react with different acid components of the vitelline membrane and the lamellae and in this way bring
about the solidifying linkages.
The situation in the solidified membrane may, however, be a more
complicated one. It has been recorded above that even the connections
between the filaments of the lamellae are sensitive to reduced glutathione.
The delayed lamellae had a more open structure when ribonucleasetreated eggs underwent a subsequent treatment with reduced glutathione.
It may be remembered also that both thioglycolic acid and cysteine
prevent the hardening of the elevating fertilization membrane (Runnström et al, 1943). Monroy (1949) and Monroy and Runnström (1948)
showed that the solidified fertilization membrane of Psammechinus
eggs
gets softer upon treatment with thioglycolic acid at pH 6.0 and 7.5. This
indicates a reduction of SH groups. Furthermore, after pretreatment with
thioglycolic acid, the fertilization membrane became rather sensitive to
chymotrypsin (about 10~
4 Anson units), whereas the sensitivity to trypsin
of nearly the same titer was rather low. This would indicate that tyrosine
groups would be available in the fertilization membrane and that
tyrosine plays a decisive role in the stability of the fertilization membrane. Ths may depend on the reactivity of the phenol groups present
in tyrosine. It is peculiar that trypsin does not have a stronger effect
in view of the fact that the "toughening factor" seems to be a basic
protein and thus should contain arginine and lysine. This research should
be repeated with several different species as material.
It follows from the curve of Fig. 33 that Ca
2+ is also necessary for the
solidification of the membrane (see also Hobson, 1927). The Ca
2+ may be
able to bind together acid groups that have not reacted with the basic
groups of MTF.
The delayed lamellae are converted into rods or plates at the same time
as the toughening of the fertilization membrane occurs. There is also
striking simultaneity in the conversion of the delayed lamellae even when
their number is rather large (Runnström, 1948). This points definitely