A small but growing number of bacteria and phages are known to contain linear, hairpin-ended genomes. The hairpin “protelomeres” are created by the action of a dedicated enzyme known as protelomerase that acts on a palindromic DNA target sequence. Phage protelomerases are typically longer than their bacterial counterparts and contain an additional far C-terminal region of limited sequence conservation. Studies of the protelomerase of the Klebsiella oxytoca phage ΦKO2 have shown that although the far C-terminal region is not required to produce hairpin ends, truncation of the region has a drastic effect on enzyme kinetics. To date, no other studies have been reported on the far C-terminal region of this or any other protelomerase. We present the solution structures of the far C-terminal regions of two phage protelomerases. The regions form homologous, compact structures that adopt a fold similar to the canonical double-stranded RNA-binding domain and have been called the far C-terminal domains. Sequence alignment and secondary structure predictions show that all known and putative phage protelomerases contain C-terminal regions which will almost certainly form homologous domains. A sequence comparison of these proteins with all known protelomerases is presented, along with an analysis of the sequence and structure of proteins which adopt a similar fold. Based on structure homology and comparative sequence conservation of key binding regions, we propose that the domain belongs to the growing family of three stranded β-sheet DNA-binding proteins that is a subclass of the double-stranded RNA-binding domain superfamily.
|Advisor:||Davis, Darrell R.|
|Commitee:||Ireland, Chris, Kay, Michael, Schmidt, Eric, Sundquist, Wes|
|School:||The University of Utah|
|School Location:||United States -- Utah|
|Source:||DAI-B 72/04, Dissertation Abstracts International|
|Keywords:||C-terminal domains, Double-stranded RNA-binding domain, Protelomerases|
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