An avidin-like domain that does not bind biotin is adopted for oligomerization by the extracellular mosaic protein fibropellin

Biomedical Engineering Department, 44 Cummington Street, Boston University, Boston, MA 02215, USA.
Protein Science (Impact Factor: 2.85). 03/2005; 14(2):417-23. DOI: 10.1110/ps.04898705
Source: PubMed


The protein avidin found in egg white seems optimized for binding the small vitamin biotin as a stable homotetramer. Indeed, along with its streptavidin ortholog in the bacterium Streptomyces avidinii, this protein shows the strongest known noncovalent bond of a protein with a small ligand. A third known member of the avidin family, as similar to avidin as is streptavidin, is found at the C-terminal ends of the multidomain fibropellin proteins found in sea urchin. The fibropellins form a layer known as the apical lamina that surrounds the sea urchin embryo throughout development. Based upon the structure of avidin, we deduced a structural model for the avidin-like domain of the fibropellins and found that computational modeling predicts a lack of biotin binding and the preservation of tetramerization. To test this prediction we expressed and purified the fibropellin avidin-like domain and found it indeed to be a homotetramer incapable of binding biotin. Several lines of evidence suggest that the avidin-like domain causes the entire fibropellin protein to tetramerize. We suggest that the presence of the avidin-like domain serves a structural (tetrameric form) rather than functional (biotin-binding) role and may therefore be a molecular instance of exaptation-the modification of an existing function toward a new function. Finally, based upon the oligomerization of the avidin-like domain, we propose a model for the overall structure of the apical lamina.

Download full-text


Available from: Itai Yanai,
  • Source

  • [Show abstract] [Hide abstract]
    ABSTRACT: The eggs and cleavage stage embryos of many animals express integrins and signal transduction components, yet comparatively little is known of the signaling complexes formed or the role of integrin signaling in early development. Genomic approaches have revealed the complement of integrin signaling components expressed in early sea urchin development. We review what is known about the distribution and function of integrins, integrin ligands, and integrin signal transduction proteins expressed during this critical phase of development. Immediately after fertilization integrins are expressed on the apical surface of the egg where the receptors interact with several potential ligands in the hyaline layer. The apical integrin complex is essential for reorganization of the egg cortex. During cleavage the blastocoel forms and a second integrin complex forms on the basal surface of blastomeres interacting with basal lamina components of the extracellular matrix. The integrin subunits of the apical and basal complexes differ and localization data indicate the apical and basal complexes may contain different scaffolding proteins and different kinases. We propose that there are two independent integrin-based signaling complexes formed during cleavage and blastula formation that may have distinct and essential functions in early development. The sea urchin is an excellent model for studies of these pathways and a number of approaches are available to determine their roles in early development.
    Signal Transduction 04/2007; 7(2):207 - 215. DOI:10.1002/sita.200600120
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Because of the compelling need for manufacturing micro- to nano-scale structures, researchers are actively investigating new methods that are applicable for small scale manufacturing. Among them, optical tweezers that can manipulate microscopic objects using a laser are receiving key attention. Optical tweezers have been used actively in the field of science. For example, they were used for measuring mechanical characteristics on the scale of piconewtons or for manipulating and sorting large numbers of particles. However, little work has been reported on 'manufacturing' objects. In this paper, we present a new method for manufacturing micro-scale structures using micro-scale polystyrene particles. Particles will be controlled with a user interface that utilizes a human hand and glued together by the bonding force between biotin and streptavidin.
    Journal of Micromechanics and Microengineering 09/2007; 17(10):N82. DOI:10.1088/0960-1317/17/10/N03 · 1.73 Impact Factor
Show more