Structural highlights
Function[NPM2_HUMAN] Core histones chaperone involved in chromatin reprogramming, specially during fertilization and early embryonic development. Probably involved in sperm DNA decondensation during fertilization.[1] Publication Abstract from PubMedHuman Npm2 is an ortholog of Xenopus nucleoplasmin (Np), a chaperone that binds histones. We have determined the crystal structure of a truncated Npm2-core at 1.9 A resolution and show that the N-terminal domains of Npm2 and Np form similar pentamers. This allowed us to model an Npm2 decamer which may be formed by hydrogen bonds between quasi-conserved residues in the interface between two pentamers. Interestingly, the Npm2 pentamer lacks a prototypical A1-acidic tract in each of its subunits. This feature may be responsible for the inability of Npm2-core to bind histones. However, Npm2 with a large acidic tract in its C-terminal tail (Npm2-A2) is able to bind histones and form large complexes. Fluorescence resonance energy transfer experiments and biochemical analysis of loop mutations support the premise that nucleoplasmins form decamers when they bind H2A-H2B dimers and H3-H4 tetramers simultaneously. In the absence of histone tetramers, these chaperones bind H2A-H2B dimers with a single pentamer forming the central hub. When taken together, our data provide insights into the mechanism of histone binding by nucleoplasmins. Crystal Structure and Function of Human Nucleoplasmin (Npm2): A Histone Chaperone in Oocytes and Embryos.,Platonova O, Akey IV, Head JF, Akey CW Biochemistry. 2011 Sep 20;50(37):8078-8089. Epub 2011 Aug 24. PMID:21863821[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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