SOME PROTEIN PROPERTIES IMPORTANT FOR ENZYME CATALYSIS - New Trends in Enzyme Catalysis and Biomimetic Chemical Reactions - page 146

amorphous regions. Thus, the block system is embedded in a viscous amorphous
medium. The globule is surrounded by a glycerol-like sheath composed of exposed
surface groups and water molecules. The concept of proteins as systems possessing the
properties of amorphous, glassy bodies was developed on the basis of data on the
temperature dependency of the heat capacity in the region of helium temperature
(Goldansky et al., 1983), as well as theoretical considerations (Shaitan et al., 2001;
Vitkup et al., 2000). Analogous concepts were worked out for protein bodies, such as
rubber-like systems (Lumry and Gregory, 1986).

4.1.7. PROTEINS DYNAMICS AND THEIR FUNCTIONAL ACTIVITY

Data on transglobular transitions at substrate-enzyme and substrate analogue-enzyme
interactions and the considerable body of other evidence of such effects on other proteins
indicate that the capacity of a protein globule to change conformation as a result of
intramolecular dynamics is an inherent property of these macromolecules. It was
suggested that the processes of complex formation between antigens and antibodies such
as allosteric transitions, mechanical transformations, electron transfer, etc., only occurred
because of the ability of protein globules to quickly and reversibly change their
conformation (Lumry and Eyring, 1954; Lamry and Biltonen, 1969; Lumry and
Rajender, 1970; Likhtenshtein, 1966, 1976a, b; Amadei et al., 1993; Faber and Mathews,
1990; Karplus and Petsko, 1990; Zhou et al., 1998; Schulten,, 2000). More detailed
information on the role of protein dynamics was obtained from experiments in which the
dependence of kinetic parameters of functional activity and the stability of proteins and
enzymes were compared to the quantitative parameters of various dynamical modes.
In the search for such a correlation, was modified by a spin label
attached to the methionine-92 group in the region of the active site and by a M ssbauer

label in the enzyme globule periphery (Likhtenshtein, 1976b, 1988; Frolov et al., 1978;
Krinichny et al., 1987). The protein tryptophane group also served as an intrinsic
fluorescence label. Agitation of the label mobility in the nanosecond region at relative
humidity about correlates with a sharp increase in the hydrolysis degree of the
cyanomoyl covalent compound (Roslyakov and Churgin, 1972). This
result highlighted the significance of nanosecond dynamics in the chemical step of the
enzyme reaction.
Photosensitive systems are convenient objects for analysing a possible correlation
between the dynamic and functional properties of proteins. After a short light pulse, it is
possible to observe a chemical reaction and to trace the dynamical state of the matrix
with the aid of internal and external physical labels.
The dynamic state of sperm-whale myoglobin monitored by spin, fluorescence, and
Mössbauer labels (Likhtenshtein, 1988, 1993) as a function of temperature was
compared with the results of kinetic studies on the photodissociation and reassociation of
CO-deoxymyoglobin (Frauenfelder et al, 1991). The three independent labelling
methods showed sharp increases in nanosecond mobility in the vicinity of the label in a
temperature region of approximately 200-220 K. These temperatures were close to the
temperatures

ö

of the dramatic increases in the relative quantum yield of the

photodissociation, as well as to the fraction of non-dissociated molecules for s