The three-dimensional structure of CsmA: A small antenna protein from the green sulfur bacterium Chlorobium tepidum

Pedersen, Marie Østergaard; Underhaug, Jarl; Dittmer, Jens; Miller, Mette; Nielsen, Niels Chr.

doi:10.1016/j.febslet.2008.07.020

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Volume 582, Issue 19 , Pages 2869-2874, 20 August 2008

The three-dimensional structure of CsmA: A small antenna protein from the green sulfur bacterium Chlorobium tepidum

Edited by Richard Cogdell

Marie Østergaard Pedersen
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
Jarl Underhaug
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
Jens Dittmer
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
- Corresponding authors. Fax: +45 86 196199.
Mette Miller
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
Niels Chr. Nielsen
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark
- Corresponding authors. Fax: +45 86 196199.

Received 26 May 2008; received in revised form 25 June 2008; accepted 12 July 2008. published online 22 July 2008.

Abstract

The structure of the chlorosome baseplate protein CsmA from Chlorobium tepidum in a 1:1 chloroform:methanol solution was determined using liquid-state NMR spectroscopy. The data reveal that the 59-residue protein is predominantly α-helical with a long helical domain extending from residues V6 to L36, containing a putative bacteriochlorophyll a binding domain, and a short helix in the C-terminal part extending from residues M41 to G49. These elements are compatible with a model of CsmA having the long N-terminal α-helical stretch immersed into the lipid monolayer confining the chlorosome and the short C-terminal helix protruding outwards, thus available for interaction with the Fenna–Matthews–Olson antenna protein.

Keywords: Chlorosome, CsmA, Green bacterium, Nuclear magnetic resonance, Photosynthetic antenna, Chlorobium tepidum