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Biomedical subjects

D G George

Publications and source records attributed to D G George.

52 records · Page 3Linked to original sources
PubMed1985

New perspectives on bacterial ferredoxin evolution.

Recent evidence indicates that a gene transposition event occurred during the evolution of the bacterial ferredoxins subsequent to the ancestral intrasequence gene duplication. In light of this new information, the relationships among the bacterial ferredoxins were reexamined and an evolutionary tree consistent with this new understanding was derived. The bacterial ferredoxins can be divided into several groups based on their sequence properties; these include the clostridial-type ferredoxins, the Azotobacter-type ferredoxins, and a group containing the ferredoxins from the anaerobic, green, and purple sulfur bacteria. Based on sequence comparison, it was concluded that the amino-terminal domain of the Azotobacter-type ferredoxins, which contains the novel 3Fe:3S cluster binding site, is homologous with the carboxyl-terminal domain of the ferredoxins from the anaerobic photosynthetic bacteria. A number of ferredoxin sequences do not fit into any of the groups described above. Based on sequence properties, these sequences can be separated into three groups: a group containing Methanosarcina barkeri ferredoxin and Desulfovibrio desulfuricans ferredoxin II, a group containing Desulfovibrio gigas ferredoxin and Clostridium thermoaceticum ferredoxin, and a group containing Desulfovibrio africanus ferredoxin I and Bacillus stearothermophilus ferredoxin. The last two groups differ from all of the other bacterial ferredoxins in that they bind only one Fe:S cluster per polypeptide, whereas the others bind two. Sequence examination indicates that the second binding site has been either partially or completely lost from these ferredoxins. Methanosarcina barkeri ferredoxin and Desulfovibrio desulfuricans ferredoxin II are of interest because, of all the ferredoxins whose sequences are presently known, they show the strongest evidence of internal gene duplication.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1985

The prokaryote-eukaryote interface.

Over the past 30 years the study of the sequences of proteins and nucleic acids has produced almost incredible amounts of information, new concepts, and new avenues of research. The beginning was slow: the first peptide hormones sequenced in the early 1950's, the first cytochrome c (horse) in 1961, the first bacterial ferredoxin in 1964, and the first transfer RNA (yeast alanine tRNA) in 1965. In the past 6 years, the rate of data accumulation has accelerated tremendously, primarily due to technological advances in nucleic acid sequencing techniques. For investigators of biological evolution, the sequence data and the new information on genetic mechanisms would prove to be the best evidence for elucidating relationships among the genomes of living organisms and for deducing phylogenetic history. In particular, they needed evidence to decide between the two hypotheses for the origin of eukaryotic cells. Now, less than 20 years since Margulis renewed the investigation of this problem, comparisons of protein and nucleic acid sequences, especially of the small subunit ribosomal RNAs, have answered this question in favor of the endosymbiotic origin of eukaryotic cells. After briefly discussing some of the concepts that helped resolve this controversy and the problems involved in using sequence data for evolutionary studies, we describe a few examples of useful evolutionary trees.

Amino Acid Sequence↗
PubMed1984

Identification of the probable coding region for exon 2 of cytochrome oxidase polypeptide I from Aspergillus nidulans mitochondrion.

Hypothetical protein URFe of Aspergillus nidulans mitochondrion is homologous with the amino end of cytochrome oxidase (EC 1.9.3.1) polypeptide I. Unidentified reading frame URFe does not contain a suitable initiation codon and codes for a protein with a length of only 91 residues, corresponding to about 20% of cytochrome oxidase polypeptide I. It is proposed that this region codes for the second exon of the cox 1 gene of Aspergillus mitochondrion. Possible candidates for the 2- to 3-residue amino-terminal exon 1 are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Ragweed allergen Ra3: relationship to some type 1 copper-binding proteins.

We have found ragweed allergen Ra3 to be related to the type 1 copper proteins; it is most closely related to stellacyanin and basic blue protein. The type 1 copper proteins form a diverse group of proteins, most of which are involved in electron transport. However, key amino acids believed to be involved in copper binding are absent from the allergen sequence; thus, the allergen is not likely to be functionally related to the type 1 copper proteins. We have grouped these proteins into one superfamily and we depict the relationships among them by an evolutionary tree. As indicated by this tree, an ancient gene duplication resulted in the divergence of plastocyanin from the line leading to basic blue protein, stellacyanin, and allergen Ra3.

Allergens↗