Chemical cross-linking of the chloroplast localized small heat-shock protein, Hsp21, and the model substrate citrate synthase

Research output: Contribution to journalArticle

Abstract

The molecular mechanism whereby the small heat-shock protein ( sHsp) chaperones interact with and prevent aggregation of other proteins is not fully understood. We have characterized the sHsp-substrate protein interaction at normal and increased temperatures utilizing a model substrate protein, citrate synthase ( CS), widely used in chaperone assays, and a dodecameric plant sHsp, Hsp21, by chemical cross-linking with 3,39-Dithiobis[sulfosuccinimidylpropionate] (DTSSP) and mass spectrometric peptide mapping. In the absence of CS, the cross- linker captured Hsp21 in dodecameric form, even at increased temperature ( 47 C). In the presence of equimolar amounts of CS, no Hsp21 dodecamer was captured, indicating a substrate-induced Hsp21 dodecamer dissociation by equimolar amounts of CS. Cross-linked Hsp21-Hsp21 dipeptides indicated an exposure of the Hsp21 C-terminal tails and substrate-binding sites normally covered by the C terminus. Cross-linked Hsp21-CS dipeptides mapped to several sites on the surface of the CS dimer, indicating that there are numerous weak and short-lived interactions between Hsp21 and CS, even at normal temperatures. The N-terminal arms especially interacted with a motif in the CS dimer, which is absent in thermostable forms of CS. The cross-linking data suggest that the presence of substrate rather than temperature influences the conformation of Hsp21.

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Subject classification (UKÄ) – MANDATORY

  • Biological Sciences

Keywords

  • heat-shock protein, small, chemical cross-linking, mass spectrometric peptide mapping, protein-protein interactions, citrate synthase
Original languageEnglish
Pages (from-to)1464-1478
JournalProtein Science
Volume16
Issue number7
Publication statusPublished - 2007
Publication categoryResearch
Peer-reviewedYes

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