@article{TEXTUAL,
      recid = {10200},
      author = {Jin, Tianquan and Ito, Yoshihiro and Luan, Xianghong and  Dangaria, Smit and Walker, Cameron and Allen, Michael and  Kulkarni, Ashok and Gibson, Carolyn and Braatz, Richard and  Liao, Xiubei and Diekwisch, Thomas G. H.},
      title = {Elongated Polyproline Motifs Facilitate Enamel Evolution  through Matrix Subunit Compaction},
      journal = {PLOS Biology},
      address = {2009-12-22},
      number = {TEXTUAL},
      abstract = {<p>Vertebrate body designs rely on hydroxyapatite as the  principal mineral component of relatively light-weight,  articulated endoskeletons and sophisticated tooth-bearing  jaws, facilitating rapid movement and efficient predation.  Biological mineralization and skeletal growth are  frequently accomplished through proteins containing  polyproline repeat elements. Through their well-defined yet  mobile and flexible structure polyproline-rich proteins  control mineral shape and contribute many other biological  functions including Alzheimer's amyloid aggregation and  prolamine plant storage. In the present study we have  hypothesized that polyproline repeat proteins exert their  control over biological events such as mineral growth,  plaque aggregation, or viscous adhesion by altering the  length of their central repeat domain, resulting in  dramatic changes in supramolecular assembly dimensions. In  order to test our hypothesis, we have used the vertebrate  mineralization protein amelogenin as an exemplar and  determined the biological effect of the four-fold increased  polyproline tandem repeat length in the amphibian/mammalian  transition. To study the effect of polyproline repeat  length on matrix assembly, protein structure, and apatite  crystal growth, we have measured supramolecular assembly  dimensions in various vertebrates using atomic force  microscopy, tested the effect of protein assemblies on  crystal growth by electron microscopy, generated a  transgenic mouse model to examine the effect of an  abbreviated polyproline sequence on crystal growth, and  determined the structure of polyproline repeat elements  using 3D NMR. Our study shows that an increase in PXX/PXQ  tandem repeat motif length results (i) in a compaction of  protein matrix subunit dimensions, (ii) reduced  conformational variability, (iii) an increase in  polyproline II helices, and (iv) promotion of apatite  crystal length. Together, these findings establish a direct  relationship between polyproline tandem repeat fragment  assemblies and the evolution and the design of vertebrate  mineralized tissue microstructures. Our findings reveal  that in the greater context of chordate evolution, the  biological control of apatite growth by polyproline-based  matrix assemblies provides a molecular basis for the  evolution of the vertebrate body plan.</p>},
      url = {http://knowledge.uchicago.edu/record/10200},
}