Mecky Pohlschröder

Associate Professor of Biology
201 Leidy Laboratories
pohlschr@sas.upenn.edu
215-573-2283
Evolution
Microbiology
Cell and Developmental Biology
Computational Biology
Education: 

Vordiplom, Universität of Münster, Germany, 1988

Ph.D. UMass, Amherst, 1994

Postdoc. Harvard Medical School, 1994-1998

Research Interests: 
Although cells synthesize all of their proteins in the cytoplasm, countless cellular processes depend on secreted proteins that perform their functions in the extracytoplasmic environment where they play key roles in many basic biological processes, including energy generation, nutrient uptake, and motility. In bacteria and archaea, the two prokaryotic domains of life, the majority of proteins are believed to be secreted either in an unfolded conformation via the universally conserved Sec pathway or in a folded conformation via the Twin arginine transport (Tat) pathway (Fig. 1). During protein translation at the ribosome, the presence of Sec or Tat signal sequences at the N-terminus of the nascent protein target it for translocation across the cytoplasmic membrane. Some of these proteins, including toxins and proteins involved in intercellular communication, are ultimately released into the extracellular environment, but most remain associated with the cell surface.
Our lab has focused on characterizing protein transport in archaea, prokaryotes that have Sec machinery more closely resembling that of eukaryotes than bacteria. However, some aspects of protein transport are very similar in the two prokaryotic domains. Studying archaeal protein transport, which also exhibits characteristics unique to archaea, has allowed us to glean important insights into the biological processes that sustain these highly intriguing organisms, many of which are adapted to life in extreme environments. Moreover, our data provides a solid foundation for the development of a deeper understanding of the evolution of protein transport.

 

Figure 1. Subcellular localization of secreted proteins. Upon secretion and signal peptide processing, Sec and Tat substrates can be released into the extracellular milieu (1), be embedded into the cytoplasmic membrane (CM) via a lipid anchor (2) or a C-terminal transmembrane segment (3). In silico data also suggest that some Sec substrates are anchored to the cell wall (CW) (4) and a number of type IV pilin-like proteins have been shown to assemble into cell appendages (5).

 In recent years, we have also focused on characterizing the diversity of Sec and Tat substrates, including substrate functions and subcellular localization. We have identified and confirmed, experimentally, substrate sequences targeted for post-translational modifications, and determined some of the components involved in these modifications. Our in vivo analyses generated information that has allowed us to develop novel subcellular localization prediction programs, as well as improve existing ones, and has led to the identification of novel Hfx. volcanii protein transport components. Further evaluation of combined in vivo and in silico data revealed intriguing patterns suggesting that evolutionary pressures may have determined the use of a specific transport pathway and surface anchoring mechanisms for some substrates.

Selected Publications: 

Click on PubMed link for Dr. Pohlschroder's publications.

Courses Taught: 

BIOL 375 - Microbial Diversity and Pathogenesis

BIOL 376 - Microbial Divesity and Pathogenesis Lab