PHYLOGENETIC ANALYSIS OF CARBAMOYLPHOSPHATE SYNTHETASE GENES - COMPLEX EVOLUTIONARY HISTORY INCLUDES AN INTERNAL DUPLICATION WITHIN A GENE WHICH CAN ROOT THE TREE OF LIFE
Fs. Lawson et al., PHYLOGENETIC ANALYSIS OF CARBAMOYLPHOSPHATE SYNTHETASE GENES - COMPLEX EVOLUTIONARY HISTORY INCLUDES AN INTERNAL DUPLICATION WITHIN A GENE WHICH CAN ROOT THE TREE OF LIFE, Molecular biology and evolution, 13(7), 1996, pp. 970-977
Carbamoylphosphate synthetase (CPS) catalyzes the first committed step
in pyrimidine biosynthesis, arginine biosynthesis, or the urea cycle.
Organisms may contain either one generalized or two specific CPS enzy
mes, and these enzymes may be heterodimeric (encoded by linked or unli
nked genes), monomeric, or part of a multifunctional protein. In order
to help elucidate the evolution of CPS, we have performed a comprehen
sive phylogenetic analysis using the 21 available complete CPS sequenc
es, including a sequence from Sulfolobus solfataricus P2 which we repo
rt in this paper. This is the first report of a complete CPS gene sequ
ence from an archaeon, and sequence analysis suggests that it encodes
an enzyme similar to heterodimeric CPSII. We confirm that internal sim
ilarity within the synthetase domain of CPS is the result of an ancien
t gene duplication that preceded the divergence of the Bacteria, Archa
ea, and Eukarya, and use this internal duplication in phylogenetic tre
e construction to root the tree of life. Our analysis indicates with h
igh confidence that this archaeal sequence is more closely related to
those of Eukarya than to those of Bacteria. In addition to this ancien
t duplication which created the synthetase domain, our phylogenetic an
alysis reveals a complex history of further gene duplications, fusions
, and other events which have played an integral part in the evolution
of CPS.