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Biomedical subjects

P R Whitehead

Publications and source records attributed to P R Whitehead.

7 recordsLinked to original sources
PubMed1986

Restriction endonucleases from Herpetosiphon giganteus: an example of the evolution of DNA recognition specificity?

We describe the partial purification and characterisation of five Type II restriction endonucleases from two strains of Herpetosiphon giganteus. One of the activities, HgiJII, was the first enzyme found that cleaves DNA at the family of related sequences 5'-G-R-G-C-Y/C-3'. This enzyme may be related to the enzyme HgiAI from a different strain of the same species, and which cleaves at the sites 5'-G-W-G-C-W/C-3'. We have shown that DNAs from the strains producing HgiAI and HgiJII are resistant to both of these restriction endonucleases. The remaining four enzymes described here share recognition and cleavage specificities with other restriction endonucleases. The evolution of Type II restriction-modification systems and their role in vivo are discussed.

Bacteroidetes↗
PubMed1985

A simple and rapid method for screening bacteria for type II restriction endonucleases: enzymes in Aphanothece halophytica.

A method is described which allows a large number of bacterial strains to be rapidly and easily screened for the presence of site-specific endonucleases. The method involves selective permeabilization of the bacterial cell and analysis of the exuded material. Type II restriction endonucleases from cyanobacteria and Gram-negative eubacteria have been detected and new enzymes have been found. The method should be widely applicable and easy to modify for use in genera other than those tested. Three-site-specific endonuclease activities, detected by this method in Aphanothece halophytica PCC 7412, were purified and their recognition and cleavage specificities were determined AhaI and AhaII recognise and cleave the same DNA sequences as CauII and AcyI respectively; the specificity of AhaIII (TTT decreases AAA) has been reported previously (Whitehead and Brown, 1982, FEBS Letters 143:296-300).

Bacteria↗
PubMed1985

Three restriction endonucleases from Anabaena flos-aquae.

Three site-specific endonucleases, AflI, AflII and AflIII, have been partially purified from the cyanobacterium Anabaena flos-aquae CCAP 1403/13f. Their recognition and cleavage specificities have been determined to be: (formula; see text) AflII and AflIII are new specificities and may be useful in molecular cloning, as well as in the analysis of DNA. The distribution of type II restriction endonucleases in the cyanobacteria is briefly discussed.

Autoradiography↗
PubMed1983

EaeI: a restriction endonuclease from Enterobacter aerogenes.

We describe the isolation and characterization of a type II restriction endonuclease from Enterobacter aerogenes. This recognises and cleaves the family of related sequences: 5'-Py-G-G-C-C-Pu-3' to generate DNA fragments with 5'-tetranucleotide extensions. EaeI may be useful in molecular cloning experiments, especially in conjunction with other enzymes which generate the same terminal extensions. Potential problems in the methods used to determine the cleavage specificity are discussed.

Bacteriophage lambda↗
PubMed1980

Nucleotide sequences at the ends of the mercury resistance transposon, Tn501.

The nucleotide sequences at the ends of the mercury-resistance transposon, Tn501, have been determined. The terminal sequences are inverted repeated sequences 38 nucleotide pairs in length, which differ in 3 nucleotide pairs. The transposon is flanked by directly repeated sequences of 5 nucleotide pairs, originating from a single pentanucleotide sequence in the recipient replicon. There is no obvious homology between recipient replicons at the site of insertion of the transposon. The structures of the ends of Tn501 are compared with those of other transposons and insertion sequences. The use of Tn501 to locate an EcoRI site within a genetically defined sequence of interest is discussed.

Base Sequence↗
PubMed1980

HgiAI: a restriction endonuclease from Herpetosiphon giganteus HP1023.

A new class II restriction endonuclease, HgiAI has been partially purified from Herpetosiphon giganteus HP1023. The enzyme activity has been characterized and shown to recognize the family of related hexanucleotide sequences (Formula: see text) where the second and fifth nucleotide pairs are A:T pairs in either orientation. Cleavage occurs as shown, to give DNA fragments with 3'-terminal tetranucleotide extensions. The recognition sites of the enzymes SacI and SstI (Formula: see text) form a subset of the recognition site of HgiAI. One of the four possible tetranucleotide 3'-extensions (cohesive ends), generated by HgiAI is identical with those generated by SacI and SstI, another is identical with that of PstI. HgiAI should be useful for molecular cloning.

Base Sequence↗