The core of chloroplast nucleoids contains architectural SWIB domain proteins

Joanna Melonek, Andrea Matros, Mirl Trösch, Hans Peter Mock, Karin Krupinska*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

50 Citations (Scopus)

Abstract

A highly enriched fraction of the transcriptionally active chromosome from chloroplasts of spinach (Spinacia oleracea) was analyzed by two-dimensional gel electrophoresis and mass spectrometry to identify proteins involved in structuring of the nucleoid core. Among such plastid nucleoid-associated candidate proteins a 12-kD SWIB (SWI/SNF complex B) domaincontaining protein was identified. It belongs to a subgroup of low molecular mass SWIB domain proteins, which in Arabidopsis thaliana has six members (SWIB-1 to SWIB-6) with predictions for localization in the two DNA-containing organelles. Green/red fluorescent protein fusions of four of them were shown to be targeted to chloroplasts, where they colocalize with each other as well as with the plastid envelope DNA binding protein in structures corresponding to plastid nucleoids. For SWIB-6 and SWIB-4, a second localization in mitochondria and nucleus, respectively, could be observed. SWIB-4 has a histone H1 motif next to the SWIB domain and was shown to bind to DNA. Moreover, the recombinant SWIB-4 protein was shown to induce compaction and condensation of nucleoids and to functionally complement a mutant of Escherichia coli lacking the histone-like nucleoid structuring protein H-NS.

Original languageEnglish
Pages (from-to)3060-3073
Number of pages14
JournalPlant Cell
Volume24
Issue number7
DOIs
Publication statusPublished - Jul 2012
Externally publishedYes

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