comparative analysis of two conserved motifs in bacterial poly(A) polymerase and CCA-adding enzyme

Showing a high sequence similarity, the evolutionary closely related bacterial poly(A) polymerases (PAP) and CCA-adding enzymes catalyze quite different reactions--PAP adds poly(A) tails to RNA 3'-ends, while CCA-adding enzymes synthesize the sequence CCA at the 3'-terminus of tRNAs. Here,...

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Bibliographic Details
Published in:Nucleic acids research 2008-09, Vol.36 (16), p.5212-5220
Main Authors: Just, Andrea, Butter, Falk, Trenkmann, Michelle, Heitkam, Tony, Mörl, Mario, Betat, Heike
Format: Article
Language:English
Subjects:
Amino Acid Motifs
Amino Acid Sequence
Amino Acid Substitution
Conserved Sequence
Escherichia coli
Escherichia coli - enzymology
Escherichia coli Proteins - chemistry
Escherichia coli Proteins - genetics
Escherichia coli Proteins - metabolism
Molecular Sequence Data
Nucleic Acid Enzymes
Nucleotides - metabolism
Polyadenylation
Polynucleotide Adenylyltransferase - chemistry
Polynucleotide Adenylyltransferase - genetics
Polynucleotide Adenylyltransferase - metabolism
RNA Nucleotidyltransferases - chemistry
RNA Nucleotidyltransferases - genetics
RNA Nucleotidyltransferases - metabolism
Sequence Homology, Amino Acid
Substrate Specificity
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Summary:Showing a high sequence similarity, the evolutionary closely related bacterial poly(A) polymerases (PAP) and CCA-adding enzymes catalyze quite different reactions--PAP adds poly(A) tails to RNA 3'-ends, while CCA-adding enzymes synthesize the sequence CCA at the 3'-terminus of tRNAs. Here, two highly conserved structural elements of the corresponding Escherichia coli enzymes were characterized. The first element is a set of amino acids that was identified in CCA-adding enzymes as a template region determining the enzymes' specificity for CTP and ATP. The same element is also present in PAP, where it confers ATP specificity. The second investigated region corresponds to a flexible loop in CCA-adding enzymes and is involved in the incorporation of the terminal A-residue. Although, PAP seems to carry a similar flexible region, the functional relevance of this element in PAP is not known. The presented results show that the template region has an essential function in both enzymes, while the second element is surprisingly dispensable in PAP. The data support the idea that the bacterial PAP descends from CCA-adding enzymes and still carries some of the structural elements required for CCA-addition as an evolutionary relic and is now fixed in a conformation specific for A-addition.
ISSN:0305-1048
1362-4962
DOI:10.1093/nar/gkn494