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Parallel Functional Changes in the Digestive RNases of Ruminants and Colobines by Divergent Amino Acid Substitutions
- Source :
- Molecular Biology and Evolution. 20:1310-1317
- Publication Year :
- 2003
- Publisher :
- Oxford University Press (OUP), 2003.
-
Abstract
- A morphological or physiological trait may appear multiple times in evolution. At the molecular level, similar protein functions may emerge independently in different lineages. Whether these parallel functional changes are due to parallel amino acid substitutions has been a subject of debate. Here, I address this question using digestive ribonucleases (RNases) of two groups of foregut-fermenting mammals: ruminant artiodactyls and colobine monkeys. The RNase1 gene was duplicated twice in ancestral ruminants at least 40 MYA, and it was also duplicated in the douc langur, an Asian colobine, approximately 4 MYA. After duplication, similar functional changes occurred in the ruminant and monkey enzymes. Interestingly, five amino acid substitutions in ruminant RNases that are known to affect its catalytic activity against double-stranded (ds) RNA did not occur in the monkey enzyme. Rather, a similar functional change in the monkey was caused by a different set of nine substitutions. Site-directed mutagenesis was used to make three of the five ruminant-specific substitutions in the monkey enzyme. Functional assays of these mutants showed that one of the three substitutions has a similar effect in monkeys, the second has a stronger effect, and the third has an opposite effect. These results suggest that (1) an evolutionary problem can have multiple solutions, (2) the same amino acid substitution may have opposite functional effects in homologous proteins, (3) the stochastic processes of mutation and drift play an important role even at functionally important sites, and (4) protein sequences may diverge even when their functions converge.
- Subjects :
- Primates
RNase P
Molecular Sequence Data
Mutagenesis (molecular biology technique)
Biology
medicine.disease_cause
Evolution, Molecular
Ribonucleases
Sequence Homology, Nucleic Acid
Genetics
medicine
Animals
Amino Acid Sequence
Selection, Genetic
Molecular Biology
Gene
Phylogeny
Ecology, Evolution, Behavior and Systematics
RNASE1
chemistry.chemical_classification
Mutation
Base Sequence
RNA
Ribonuclease, Pancreatic
Ruminants
Protein superfamily
Amino acid
Amino Acid Substitution
Colobinae
chemistry
Mutagenesis, Site-Directed
Cattle
Subjects
Details
- ISSN :
- 15371719 and 07374038
- Volume :
- 20
- Database :
- OpenAIRE
- Journal :
- Molecular Biology and Evolution
- Accession number :
- edsair.doi.dedup.....387335a1db74110ea2b1ee1bd16af3dd