Selective binding by metalloproteins to their cognate metal ions is essential to cellular survival. How proteins originally acquired the ability to selectively bind metals and evolved a diverse array of metal-centered functions despite the availability of only a few metal-coordinating functionalities remains an open question. Using a rational design approach (Metal-Templated Interface Redesign), we describe the transformation of a monomeric electron transfer protein, cytochrome cb(562), into a tetrameric assembly ((C96)RIDC-1(4)) that stably and selectively binds Zn(2+) and displays a metal-dependent conformational change reminiscent of a signaling protein. A thorough analysis of the metal binding properties of (C96)RIDC-1(4) reveals that it can also stably harbor other divalent metals with affinities that rival (Ni(2+)) or even exceed (Cu(2+)) those of Zn(2+) on a per site basis. Nevertheless, this analysis suggests that our templating strategy simultaneously introduces an increased bias toward binding a higher number of Zn(2+) ions (four high affinity sites) versus Cu(2+) or Ni(2+) (two high affinity sites), ultimately leading to the exclusive selectivity of (C96)RIDC-1(4) for Zn(2+) over those ions. More generally, our results indicate that an initial metal-driven nucleation event followed by the formation of a stable protein architecture around the metal provides a straightforward path for generating structural and functional diversity.
We have selected a group of 100 evolved planetary nebulae (PNe) and study
Their kinematics based upon spatially-resolved, long-slit, echelle
Spectroscopy. The data have been drawn from the San Pedro M\'artir Kinematic
Catalogue of PNe (L\'opez et al. 2012). The aim is to characterize in detail
Various models of star formation rate and the possible effect of the evolution
Of cosmic metallicity under the assumption that LGRBs tend to occur in
Low-metallicity galaxies. The models of star formation rate tested in this work
Include empirical fits from observational data as well as a...
We find the r-band apparent magnitude limit, combined
With the subsequent requirement for Halpha detection leads to an incompleteness
Due to missing bright Halpha sources with faint r-band magnitudes....
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