Molecular Biology of the Archaea Chromosomes and DNA

Molecular Biology of the Archaea Chromosomes and DNA Replication DNA negative supercoil: DNA gyrase in bacteria, Histone proteins in eukaryotes. Eukaryotic histones consist of eight proteins, Archae 4 proteins (tetrasomes) and are shorter. Other features are similar to eukaryotes. In some hyperthermophal archaea, positive super helixes are formed by reverse gyrase enzyme. Denaturation of DNA at high temperature is thus prevented.

Molecular Biology of the Archaea genome replication in bacteria, there is only one origin region, and two Sulfolobus and three origin regions from Halobacterium. There are many replication origins in the eukaryotic chromosome. Archaea enzymes involved in replication are similar to eukaryotes. In all organisms, DNA polymerase is structurally divided into three groups: A, B and C. Bacteria are C (Pol III) for replication, A and B for repair; Archaea and Eukaryotes use others to replicate B in replication.

Molecular Biology of the Archaea Transcription In eukaryotes, r. RNA polymerase I, m. RNA polymerase II, t. RNA and small r. RNA polymerase III Each of these three RNA polymerases recognizes the promoter region of a particular group of genes. Most of the genes in eukaryotes are transcribed by RNA polymerase II. RNA polymerases in eukaryotes are more complex than bacteria.

Molecular Biology of the Archaea As in Bacteria, Archaea has a single RNA polymerase. This enzyme resembles the RNA polymerase II enzyme in eukaryotes rather than bacteria. This enzyme contains a 6 -8 -base AT rich TATA box (TATA box) in the promoter region before the initiation of transcription. This region is similar to the Pribnow box in bacteria.

The rifamycin antibiotic binds to the β subunit of RNA polymerase in bacteria, preventing transcription and is ineffective to archaea and eukaryotes. Amanitin chemical affects the enzyme RNA polymerase II and stops transcription in eukaryotes. The rho proteins that lead to termination of transcription in bacteria were not found in the background. Inverse repetitions, like bacteria, terminate in some Archaea.

RNA Processing In eukaryotes, the first synthesized RNA is processed to form mature m. RNA. In this process, the introns in the RNA are cut and the exons combined. In this process called splicing, a complex consisting of RNA and protein called spliceosome works. Although both prokaryotic and eukaryotic genes have intron regions, RNA is processed only in eukaryotes. The nucleus is then attached to the 5 cap end of this mature m. RNA and the poly A tail to the 3 ’end.

Ribozyme (ribonucleic acid enzyme) RNA molecules showing enzymatic activity. It was first found in their study with Sidney Altman and Thomas Cech (Tetrahymena thermophila). They won the Nobel Prize (chemistry) in 1989.

Archaea introns Archaea t. RNA and r. RNA encoding genes have introns processed in this way. A specific endoribonuclease recognizes exonintron junctions and removes introns two stages. In the first stage endonuclease is cut, in the second stage ligases are ligated. The introns in the folded t. RNA are cut at the points indicated by the arrow in figure b, forming the annular intron and the t. RNA.

Protein Sythesis There are 78 proteins in eukaryotic ribosomal RNA. Of these, 34 are found in bacteria and Archaea sites, 33 in Archaea sites, and the remaining 11 are found only in eukaryotes. Archaea translation factors are not as complex as in eukaryotes, but more similar to eukaryotes than bacteria. Shine dalgarno sequence is present in bacteria and archaea, not in eukaryotes. The first synthesized amino acid is methionine in archaea and eukaryotes.