domain

Examples of domain in the following topics:

• The Diversity of Life

  • The diversity of life can be classified within the three major domains (Bacteria, Eukarya and Archaea) using phylogenetic trees.
  • The third domain contains the eukaryotes and includes unicellular microorganisms together with the four original kingdoms (excluding bacteria).
  • Woese defined Archaea as a new domain, and this resulted in a new taxonomic tree .
  • Many organisms belonging to the Archaea domain live under extreme conditions and are called extremophiles.
  • The tree shows the separation of living organisms into three domains: Bacteria, Archaea, and Eukarya.

• Antibody Structure

  • The antibody base is known as the constant domain or constant region.
  • The constant domain, which does not bind to an antibody, is the same for all antibodies.
  • IgGs, which make up about 80 percent of all antibodies in circulation, have heavy chains that consist of one variable domain and three identical constant domains.
  • IgA and IgD also have three constant domains per heavy chain, whereas IgM and IgE each have four constant domains per heavy chain.
  • The variable domain determines binding specificity, while the constant domain of the heavy chain determines the immunological mechanism of action of the corresponding antibody class.

• Binding Initiates a Signaling Pathway

  • Each cell-surface receptor has three main components: an external ligand-binding domain, a hydrophobic membrane-spanning region, and an intracellular domain inside the cell.
  • The ligand-binding domain is also called the extracellular domain.
  • The size and extent of each of these domains vary widely, depending on the type of receptor.
  • All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site.
  • In some cases, the intracellular domain of the receptor itself is an enzyme.

• Types of Receptors

  • Each cell-surface receptor has three main components: an external ligand-binding domain (extracellular domain), a hydrophobic membrane-spanning region, and an intracellular domain inside the cell.
  • The size and extent of each of these domains vary widely, depending on the type of receptor.
  • All G-protein-linked receptors have seven transmembrane domains, but each receptor has its own specific extracellular domain and G-protein-binding site.
  • Enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme.
  • In some cases, the intracellular domain of the receptor itself is an enzyme or the enzyme-linked receptor has an intracellular domain that interacts directly with an enzyme.

• Classification of Prokaryotes

  • Based on differences in the structure of cell membranes and in rRNA, Woese and his colleagues proposed that all life on earth evolved along three lineages, called domains.
  • The domain Bacteria comprises all organisms in the kingdom Bacteria, the domain Archaea comprises the rest of the prokaryotes, and the domain Eukarya comprises all eukaryotes, including organisms in the kingdoms Animalia, Plantae, Fungi, and Protista.
  • Others have argued that the three domains of life arose simultaneously, from a set of varied cells that formed a single gene pool.
  • Two of the three domains, Bacteria and Archaea, are prokaryotic.

• Basic Structures of Prokaryotic Cells

  • Prokaryotes, found in both Domain Archaea and Bacteria, are unicellular organisms that lack membrane-bound organelles and a defined nucleus.
  • The composition of the cell wall differs significantly between the domains Bacteria and Archaea, the two domains of life into which prokaryotes are divided .
  • Bacteria and Archaea are both prokaryotes, but differ enough to be placed in separate domains.
  • An ancestor of modern Archaea is believed to have given rise to Eukarya, the third domain of life.

• The Levels of Classification

  • Taxanomic classification divides species in a hierarchical system beginning with a domain and ending with a single species.
  • Within each domain is a second category called a kingdom.
  • The kingdom Animalia stems from the Eukarya domain.
  • Dogs actually share a domain (Eukarya) with the widest diversity of organisms, including plants and butterflies.
  • Describe how taxonomic classification of organisms is accomplished and detail the levels of taxonomic classification from domain to species

• Basic Techniques in Protein Analysis

  • The premise behind the two-hybrid screen is that most eukaryotic transcription factors have modular activating and binding domains that can still activate transcription even when split into two separate fragments, as long as the fragments are brought within close proximity to each other.
  • Generally, the transcription factor is split into a DNA-binding domain (BD) and an activation domain (AD).
  • In this method, a transcription factor is split into a DNA-binding domain (BD) and an activation domain (AD).
  • The binding domain is able to bind the promoter in the absence of the activator domain, but it does not turn on transcription.

• Web, Network, and Ring of Life Models

  • The "ring of life" is a phylogenetic model where all three domains of life evolved from a pool of primitive prokaryotes .
  • Using the conditioned reconstruction algorithm, it proposes a ring-like model in which species of all three domains (Archaea, Bacteria, and Eukarya) evolved from a single pool of gene-swapping prokaryotes.
  • According to the "ring of life" phylogenetic model, the three domains of life evolved from a pool of primitive prokaryotes.

• Catabolite Activator Protein (CAP): An Activator Regulator

  • CAP is a transcriptional activator that exists as a homodimer in solution, with each subunit comprising a ligand-binding domain at the N-terminus, which is also responsible for the dimerization of the protein and a DNA-binding domain at the C-terminus.