Structural basis for the thermostability of ferredoxin from the cyanobacterium Mastigocladus laminosus

Alexander Fish, Tsafi Danieli, Itzhak Ohad, Rachel Nechushtai, Oded Livnah*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Plant-type ferredoxins (Fds) carry a single [2Fe-2S] cluster and serve as electron acceptors of photosystem I (PSI). The ferredoxin from the thermophilic cyanobacterium Mastigocladus laminosus displays optimal activity at 65°C. In order to reveal the molecular factors that confer thermostability, the crystal structure of M. laminosus Fd (mFd) was determined to 1.25 Å resolution and subsequently analyzed in comparison with four similar plant-type mesophilic ferredoxins. The topologies of the plant-type ferredoxins are similar, yet two structural determinants were identified that may account for differences in thermostability, a salt bridge network in the C-terminal region, and the flexible L1,2 loop that increases hydrophobic accessible surface area. These conclusions were verified by three mutations, i.e. substitution of L1,2 into a rigid β-turn (ΔL1,2) and two point mutations (E90S and E96S) that disrupt the salt bridge network at the C-terminal region. All three mutants have shown reduced electron transfer (ET) capabilities and [2Fe-2S] stability at high temperatures in comparison to the wild-type mFd. The results have also provided new insights into the involvement of the L1,2 loop in the Fd interactions with its electron donor, the PSI complex.

Original languageAmerican English
Pages (from-to)599-608
Number of pages10
JournalJournal of Molecular Biology
Volume350
Issue number3
DOIs
StatePublished - 15 Jul 2005

Bibliographical note

Funding Information:
This work has been supported, in part, by the Israeli Science Foundation. We thank Dr D. E. Shalev from the NMR facility, and Dr M. Lebendiker from the Protein Purification Division of the Wolfson Centre for Applied Structural Biology for their advice and support, and the ESRF staff for their assistance during data collection. We thank Dr L. Shimon and Mrs M. Berman for their suggestions and assistance.

Keywords

  • Ferredoxin
  • Photosynthesis
  • Photosystem I
  • Thermostability
  • X-ray structure

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