2003 Dr. rer. nat. (PhD) University of Kaiserslautern (Prof. Dr. E. Neuhaus)

2003-2004 Postdoc at the Graduate School: „Molecular, physiological and pharmacological analysis of cellular membrane transport“ University of Homburg (Prof. Dr. R. Zimmermann)

2004-2006 Research Associate at the University of Kaiserslautern (Prof. Dr. E. Neuhaus)

2006-2009 Juniorprofessor at the Department of Cellular Physiology, University of Kaiserslautern

since December 2009: Research Associate at the University of Kaiserslautern, Department of Plant Physiology

Major Research Interest:

1. Primary and complex plastids

Chloroplasts are characteristic organelles of plants, possess an envelope of two membranes and arose by a primary endosymbiosis between a protozoan host and a cyanobacterium (higher plant, green algae, red algae and glaucophyta). However, the engulfment of a red or a green alga by a non-photosynthetic host through a process called secondary endosymbiosis gave rise to further groups of complex chimeric eukaryotes (chloraracheans, chromalveolates). The resulting photosynthetic organelle accordingly exhibits four bounding membranes. Until now the knowledge on metabolic fluxes across the membranes of complex plastids is limited. Biochemical characterization of plastidial carrier proteins involved in energy provision (nucleotide transporters, NTTs) and in the transport of intermediates of starch metabolism will provide new insights into the cellular communication across the envelope membranes of primary and complex plastids 

2. Parasites and symbionts

Apart from plastidial nucleotide transporters (NTTs), which mediate the transport of ATP in counter exchange with ADP structurally related proteins are also present in some intracellular living bacterial species. The different biochemical characteristics of specialized NTTs enable these intracellular bacteria to exploit metabolic intermediates of the host cell. The endosymbiotic bacterium Protochlamydia amoebophila for expample possesses five NTTs essential not only for energy provision by ATP/ADP counter exchange, but also for uptake of DNA and RNA components and nucleotide derivates from the host cell. Furthermore, in Protochlamydia amoebophila corresponding biosynthetic pathways were eliminated during evolution, which led to a strict dependence of the bacterium from the host cell. 

In the next future we wish to characterize the biochemical properties of different NTTs from intracellular bacteria (and of the recently identified homologs in free living bacteria) to clarify their metabolic function. 

Selected Recent Publications:  

• Ast M*, Gruber A*, Schmitz-Esser S, Neuhaus HE, Kroth P, Horn H, Haferkamp I (2009) Diatom plastids depend on nucleotide import from the cytosol. Proc. Natl. Acad. Sci. USA 106, 3621-3626 (*both authors contributed equally to this paper)  
• Schmiz-Esser S, Haferkamp I, Knab S, Penz T, Ast M, Kohl C, Wagner M, Horn M. (2008) Lawsonia intracellularis contains a gene encoding a functional rickettsia-like ATP/ADP translocase for host exploitation. J Bacteriol 190, 5746-5752  
• Trentmann O, Horn M, Terwisscha van Scheltinga, AC, Neuhaus HE, Haferkamp I (2007) Enlightening energy parasitism by analysis of an ATP/ADP transporter from Chlamydiae. PLoS Biol 5(9): e231. doi:10.1371/journal.pbio.0050231  
• Haferkamp I, Schmitz-Esser S, Linka N, Urbany C, Collingro A, Wagner M, Neuhaus HE (2004) A candidate NAD⁺ transporter in an intracellular bacterial symbiont related to Chlamydiae. Nature 432, 622-625