Molecular evolution of snake toxins: is the functional diversity of snake toxins associated with a mechanism of accelerated evolution?
Recent studies revealed that animal toxins with unrelated biological functions often possess a similar architecture. To tentatively understand the evolutionary mechanisms that may govern this principle of functional prodigality associated with a structural economy, two complementary approaches were considered. One of them consisted of investigating the rates of mutations that occur in cDNAs and/or genes that encode a variety of toxins with the same fold. This approach was largely adopted with phospholipases A2 from Viperidae and to a lesser extent with three-fingered toxins from Elapidae and Hydrophiidae. Another approach consisted of investigating how a given fold can accommodate distinct functional topographies. Thus, a number of topologies by which three-fingered toxins exert distinct functions were investigated either by making chemical modifications and/or mutational analyses or by studying the three-dimensional structure of toxin-target complexes. This review shows that, although the two approaches are different, they commonly indicate that most if not all the surface of a snake toxin fold undergoes natural engineering, which may be associated with an accelerated rate of evolution. The biochemical process by which this phenomenon occurs remains unknown.
Ohno
M
M
Department of Chemistry, Faculty of Science, Fukuoka, Japan.
Ménez
R
R
Ogawa
T
T
Danse
J M
JM
Shimohigashi
Y
Y
Fromen
C
C
Ducancel
F
F
Zinn-Justin
S
S
Le Du
M H
MH
Boulain
J C
JC
Tamiya
T
T
Ménez
A
A
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D012910:Snake Venoms; D012911:Snakes
D012910:Snake Venoms