Biomedical subjects

K Gregg

Publications and source records attributed to K Gregg.

23 records · Page 2Linked to original sources

PubMed1984

A comparison of genomic coding sequences for feather and scale keratins: structural and evolutionary implications.

DNA sequences have been obtained for embryonic chick feather and scale keratin genes. Strong homologies exist between the protein coding regions of the two gene types and between the deduced amino acid sequences of the keratin proteins. Scale keratins are larger than feather keratins and the size difference is mainly attributable to four 13-amino acid repeats between residues 77 and 128 which compose a peptide sequence rich in glycine and tyrosine. The strong similarities between the two peptide structures for feather and scale in the homologous regions suggests a similar conformation within the protein filaments. A likely consequence is that the additional repeat region of the scale protein is located externally to the core filament. Tissue-specific features of filament aggregation may be attributable to this one striking sequence difference between the constituent proteins. It is believed that the genes share a common ancestry and that feather-like keratin genes may have evolved from a scale keratin gene by a single deletion event.

Amino Acid Sequence↗

PubMed1982

Organisation of feather keratin genes in the chick genome.

A genomic clone containing sequences of five feather keratin genes has been isolated using cDNA to chicken embryonic feather keratin mRNA as a probe. The clone probably represents part of a longer cluster of tandemly spaced genes; the genes are evenly spaced with a centre to centre separations of 3.3 kb and are transcribed from the same DNA strand, suggesting that the cluster has arisen by a series of tandem duplications. The organisation and complete sequence of the central gene has been determined. The protein encoded by the gene contains 97 amino acids and its sequence is typical of proteins of the embryonic and adult feather family. The transcript from the gene has been deduced to contain a long 3' non-coding region of 435 nucleotides and a 58 base 5' non-coding region interrupted in the gene 21 bases prior to the initiation codon by the gene's only intron of 324 bases.

Amino Acid Sequence↗

PubMed1982

Epidermal characteristics related to skin cancer susceptibility.

We have compared the basal cell labeling index and cellular architecture in samples of epidermis removed by vacuum blistering from people with or without a personal history of skin cancer. Donors with no family history of skin cancer showed a basal cell labeling index of 5.5% with a standard deviation of 1.3%. Those not personally affected but with a family history gave 4.1% +/- 0.4% but among cancer patients the value was approximately doubled to 11.5% +/- 2.7%. The proportion of cells replicating was reduced after ultraviolet irradiation, with a D0 of 40 J/m2 for UVB but no difference could be demonstrated between individuals with or without a history of skin cancer.

Autoradiography↗

PubMed1981

Frequency of U.V. induced protein-DNA crosslinks in cell lines of different sensitivities.

We have measured U.V.-induced protein-DNA crosslinking in two cultured human cell lines of different sensitivities. Using a previously published method, involving SDS-protein precipitation, we obtained a biphasic response with an initial slope of 0.6 per cent DNA J-1 m2 up to 50 J m-2 and a second-phase slope of 0.12 per cent DNA J-1 m2 with a background of 22 +/- 13 per cent. Rigorous washing of SDS-protein precipitates reduced background binding to about 5 per cent with a linear U.V. effect up to 100 J m-2 of 0.038 per cent DNA J-1 m2. Binding was judged to be covalent on the grounds of stability to boiling and represented 4.1 crosslinks pg DNA-1 J-1 m2 or 60 crosslinks cell-1 J-1 m2. Similar results were obtained for both cell lines. We conclude that the differences in U.V. survival between cell lines is not related to the extent of protein-DNA crosslinking. We have been unable to detect repair of these lesions in either cell line.

Cell Line↗

PubMed1979

Terminal transferase-like activity in human melanoma cells.

An enzyme activity, capable of attaching deoxynucleotides to single-stranded oligonucleotide primers, has been detected in extracts from cultured melanoma cells. The substrate preferences of this activity show it to be distinct from the calf thymus terminal transferase (EC 2.7.7.31).

Animals↗