Lecture 3.1 Notes

Lecture 3.1 Notes - 401 Notes Bacteria and A rchaea...

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401 Notes – 3/1/10 Bacteria and Archaea phylogenetically distinct; reflected in aspects of basic molecular biology Basic architecture of genetic same for all three domains but Archaea closer to Eukarya than to Bacteria in important details o Phylogenetic kinships determined by rRNA analyses also reflected in wide variety of mechanistic attributes. Chromosomes and DNA replication Bacterial and archaeal chromosomes both circular and of same size range (complexity) However, Archaea more similar to Eukarya in chromosome packaging and details of DNA replication o Bacteria : superhelicity introduced by DNA gyrase o Eukarya : DNA packaged around histones (basic proteins specialized for packaging) o Archaea : both DNA gyrase and histones Hyperthermophiles also have reverse DNA gyrase: introduction of positive superhelicity o DNA replication: Archaea have bidirectional DNA replication like Bacteria but multiple origins of replication like Eukarya Phylogenetic and structural features of proteins involved with DNA replication show strong kinship between Archaea and Eukarya that is distinct from Bacteria (Table 8.1) Transcription and RNA processing Archaea have simplified version of eukaryotic transcription apparatus, however, regulatory strategies more closely shared with Bacteria o RNAP structure: Eukarya have 3 RNA polymerases, Archaea and Bacteria only one, however, RNAP from Archaea more closely related to RNAP II from Eukarya than to RNAP from Bacteria o Promoter recognition: Archaea more similar to Eukarya Transcription factors required for promoter recognition: BRE, TATA and INIT a simpler version of multiple factors required for eukaryotic promoter recognition.
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Intervening sequences o RNA splicing very common in Eukarya and very rare in Bacteria and Archaea Archaeal splicing mechanism used in Eukarya for very small subset of spliced genes where most RNAs are spliced by spliceosomes (which are not found in Archaea ) Protein synthesis rRNA phylogenies previously discussed Of the 78 eukaryotic ribosomal proteins: 34 common to all 3 domains, 33 shared by Archaea , 11 unique to Eukarya , none common to only Bacteria and Eukarya Initiator amino acid: Met in Eukarya and Archaea ; f-Met in Bacteria Polycistronic RNA in
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Lecture 3.1 Notes - 401 Notes Bacteria and A rchaea...

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