Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasmids from Chlamydia trachomatis LGV-434 (serotype L2) and Chlamydia psittaci meningopneumonitis strain Cal-10 were cloned into the BamHI and EcoRI sites of pBR322, respectively. The recombinant plasmids pCTL2 and pCPMn, each containing an entire respective chlamydial plasmid, were transformed into Escherichia coli. The sizes of the plasmids of C. trachomatis and C. psittaci were 7.3 and 6.2 kilobases, respectively. The two plasmids were found to be distinct by restriction endonuclease analysis, DNA-DNA hybridization, and electron microscopic heteroduplex analysis. However, partial homology was observed between restriction fragments of pCTL2 and pCPMn by Southern blot analysis. Polypeptide products encoded by these plasmids were synthesized in vitro by an E. coli-directed transcription-translation system and in vivo in E. coli maxicells and minicells. None of these polypeptides was immunoreactive with anti-chlamydial sera by immunoblotting or immunoprecipitation. Based on the comparative analysis data, the C. trachomatis and C. psittaci plasmids were found to share little genetic relatedness.
 ...
PMID:Molecular characterization of Chlamydia trachomatis and Chlamydia psittaci plasmids. 394 8

EcoHK31I DNA methyltransferase recognizes the sequence 5'-YGGCCR-3' and adds a methyl group to the fifth position of the internal cytosine to protect the DNA from cleavage by its cognate endonuclease. M.EcoHK31I is composed of polypeptides alpha and beta. Polypeptide beta only contains the conserved IX motif of the C5-MTase family, and provides a unique example to show that this motif alone may be dislocated to another polypeptide. By electromobility shift assay, we found that the alpha/beta complex recognizes specific oligonucleotide substrates. Polypeptide alpha formed aggregates with DNA, while polypeptide beta alone did not bind DNA. Therefore, polypeptide beta assists in the proper binding of polypeptide alpha to DNA substrate. The complex of polypeptide alpha and a polypeptide beta variant with an N-terminal deletion of 41 amino acids showed a 16-fold reduction in methylation activity. Further deletion resulted in an inactive methyltransferase. The dissociation equilibrium constant (Kd) of the alpha/beta complex was 56.4 nM, while the Kd value for the alpha/deltaN46-polypeptide beta complex was increased approximately 95-fold, caused by a drastic decrease in dissociate rate constant (kd) and an increase in the association rate constant (ka). This indicates that the N-terminal region of polypeptide beta takes part in subunit interaction, while the C-terminal region is involved in DNA binding.
 ...
PMID:Functional studies of the small subunit of EcoHK31I DNA methyltransferase. 1674 Jan 21

LlaGI is a single polypeptide restriction-modification enzyme encoded on the naturally-occurring plasmid pEW104 isolated from Lactococcus lactis ssp. cremoris W10. Bioinformatics analysis suggests that the enzyme contains domains characteristic of an mrr endonuclease, a superfamily 2 DNA helicase and a gamma-family adenine methyltransferase. LlaGI was expressed and purified from a recombinant clone and its properties characterised. An asymmetric recognition sequence was identified, 5'-CTnGAyG-3' (where n is A, G, C or T and y is C or T). Methylation of the recognition site occurred on only one strand (the non-degenerate dA residue of 5'-CrTCnAG-3' being methylated at the N6 position). Double strand DNA breaks at distant, random sites were only observed when two head-to-head oriented, unmethylated copies of the site were present; single sites or pairs in tail-to-tail or head-to-tail repeat only supported a DNA nicking activity. dsDNA nuclease activity was dependent upon the presence of ATP or dATP. Our results are consistent with a directional long-range communication mechanism that is necessitated by the partial site methylation. In the accompanying manuscript [Smith et al. (2009) The single polypeptide restriction-modification enzyme LlaGI is a self-contained molecular motor that translocates DNA loops], we demonstrate that this communication is via 1-dimensional DNA loop translocation. On the basis of this data and that in the third accompanying manuscript [Smith et al. (2009) An Mrr-family nuclease motif in the single polypeptide restriction-modification enzyme LlaGI], we propose that LlaGI is the prototype of a new sub-classification of Restriction-Modification enzymes, named Type I SP (for Single Polypeptide).
 ...
PMID:DNA cleavage and methylation specificity of the single polypeptide restriction-modification enzyme LlaGI. 1980 36