Taxonomic distribution of proteins containing ZnF_CHCC domains

The tree below includes only several representative species and genera. The complete taxonomic breakdown of all proteins containing ZnF_CHCC domains can be accessed here. Click the counts or percentage values to display the corresponding proteins.

Cloning and analysis of the dnaG gene encoding Pseudomonas putida DNA primase.

Szafranski P, Smith CL, Cantor CR
Biochim Biophys Acta. 1997; 1352: 243-8

The dnaG gene coding for primase, a key enzyme in DNA replication, has been isolated from chromosomal DNA of the soil bacterium Pseudomonas putida. It maps within the putative MMS operon, between the rpsU and rpoD genes. Comparison of the deduced amino acid sequence of P. putida DnaG with sequences of other known bacterial primases reveals the presence of a possible regulatory region which would be unique to pseudomonads. The analysis of nucleotide sequence suggests that stable folding of the dnaG mRNA may significantly contribute to the low level of its expression within a cell.

DNA sequence, structure and gene expression of mycobacteriophage L5: a phage system for mycobacterial genetics.

Hatfull GF, Sarkis GJ
Mol Microbiol. 1993; 7: 395-405

Genetic studies of Mycobacterium tuberculosis and other mycobacterial pathogens have suffered from the lack of a sophisticated genetic system. To address this issue we have developed a viral system through a detailed characterization of mycobacteriophage L5, a temperate phage that infects both fast- and slow-growing mycobacteria. We describe here the complete DNA sequence of the L5 genome and initial characterization of L5 virion structure and gene expression. In addition to providing a genetic 'tool-box' for the mycobacteria we find that L5 offers a new paradigm for dsDNA phages, being phenotypically temperate but employing genetic strategies for phage growth usually associated with lytic bacteriophages.

The Haemophilus influenzae dnaG sequence and conserved bacterial primase motifs.

Versalovic J, Lupski JR
Gene. 1993; 136: 281-6

The dnaG gene encodes primase which synthesizes the primer RNA essential for Escherichia coli chromosomal DNA replication. The nucleotide sequence was determined for the Haemophilus influenzae dnaG gene and used in the molecular evolutionary analysis of primases from six bacterial species. The predicted amino acid (aa) sequence of H. influenzae DnaG contains 593 residues and shares 56% identity with E. coli DnaG. The N-terminal 60% of six aligned bacterial primases contains all 71 absolutely conserved aa residues and several conserved motifs. All six bacterial primases which were sequenced contained a conserved CPFHXEKTPSF(T/S/A)VXXXKQX(F/Y)HCFGC zinc finger (zf) in the N terminus. A basic region in the N-terminal half of the primases contains a conserved motif, G(R/K)X(V/I/L)X(F/Y) (G/S/A)(G/S/A)RX(V/I/L)XXXXP, termed 'RNAP-basic', which is shared only with RNA polymerase (RNAP) large subunits. This conserved sequence represents the first motif common and specific to primases and RNAP subunits. The consensus sequence, PKYLNSPET, lies adjacent to this basic region in bacterial primases and may represent a signature sequence for bacterial DnaG. The C-terminal regions of these primases do not appear to share primary sequence similarities. These findings support our hypothesis that the primase active site of DnaG is located in the N-terminal 60% of the enzyme.

Enriched sources of Escherichia coli replication proteins. The dnaG primase is a zinc metalloprotein.

Stamford NP, Lilley PE, Dixon NE
Biochim Biophys Acta. 1992; 1132: 17-25

Primase, the product of the Escherichia coli dnaG gene, is the enzyme responsible for RNA primer synthesis on both template strands at replication forks during chromosomal DNA synthesis. The dnaG gene was modified by replacement of the natural ribosome-binding site with one complementary to the 3' end of 16S rRNA, and then inserted downstream of tandem bacteriophage lambda PR and PL promoters in the pUC9-derived vector pCE30. Following thermal induction of transcription, the resulting plasmid pPL195 directed synthesis of primase activity to levels corresponding to approx. 120,000 molecules per cell. The overproduced protein was soluble and was readily purified in high yield (31 mg per 1 of culture). Purified primase was monomeric, was fully active in priming replication at the bacteriophage G4 complementary strand origin, and was shown to contain 0.92 +/- 0.08 g atom of tightly-bound zinc per mol of protein. Potential zinc-binding amino-acid residues near the N-terminus of the protein were identified. Although a mutant primase lacking 27 amino acid residues from the N-terminus was partly soluble, it was completely inactive.