Email: gierasch@biochem.umass.edu
L. Gierasch Biochemistry & Molecular Biology Web Site
L. Gierasch Lab Web Site

Ph.D.: Harvard University
Honors: A.P. Sloan Fellowship; Vincent du Vigneaud Award for Young Investigators in Peptide Chemistry; Guggenheim Fellowship; Fellow, American Association for the Advancement of Science

Biophysical Approaches to Protein Folding and Localization

The protein folding problem, namely how amino acid sequence determines the three-dimensional structure of a protein, is not fully understood despite many years of effort. We are addressing this problem in a variety of ways in our laboratory: We study the conformational preferences of model peptides in order to explore how local sequence guides folding. We are also carrying out detailed studies in the in vitro folding of a predominantly b -sheet protein with a very simple topology. Methods we use in all of our folding work include circular dichroism, fluorescence, and nuclear magnetic resonance.

We are also interested in how a protein folds in vivo. In recent years, a class of proteins called molecular chaperones has been found to facilitate protein folding in vivo. We are addressing several questions concerning chaperones: How do they recognize and bind incompletely folded polypeptides? Do different classes of chaperones bind to their substrates in distinct ways? How do chaperones interact with their co-chaperones? Is the mechanism of chaperone-mediated folding different from that of the isolated protein?

Many proteins that are synthesized on cytoplasmic ribosomes are destined to function in non-cytoplasmic locations. We are interested in how the newly synthesized chain is directed to either extracellular or organellar sites. We have extensively examined biophysical properties of signal sequences, which facilitate the export of bacterial proteins, to elucidate their mode of action in vivo. We are now studying the interaction of signal sequences with proteins of the export pathway, including the bacterial proteins SecA and Ffh.

Representative publications:

K. S. Rotondi and L. M. Gierasch, Natural Polypeptide Scaffolds: b-Sheets, b-Turns, and b-Hairpins, Peptide Science, 84, 13-22 (2006).

J. F. Swain, E. G. Schulz, and L. M. Gierasch, Direct Comparison of a Stable Isolated Hsp70 Substrate-binding Domain in the Empty and Substrate-bound States, J. Biol. Chem., 281, 1605-11 (2006).

J. F. Swain and L. M. Gierasch, The Changing Landscape of Protein Allostery. Curr. Opin. Struct. Biol. 16, 102-108 (2006).

A. C. Marcelino, R. G. Smock, and L. M. Gierasch, Evolutionary Coupling of Structural and Functional Sequence Information in the Intracellular Lipid-Binding Protein Family, Proteins: Structure Function Bioinformatics, 63, 373-384 (2006).

Z. Ignatova and L. M. Gierasch, Extended PolyQ Tracts Cause Aggregation and Structural Perturbation of a Neighboring b–Barrel Protein, J. Biol. Chem., 281, 12959-67 (2006).

L. F. Cavanaugh, A. G. Palmer III, L. M. Gierasch, and J. F. Hunt, Disorder Breathes Life into a DEAD Motor, Nature Struct. Mol. Biology, 13, 566-569 (2006).

Z. Ignatova and L. M. Gierasch, The Natural Osmolyte Proline Prevents Protein Aggregation In Vitro and In Vivo, Proc. Natl. Acad. Sci. USA, 103, 13357-61 (2006).

I. L. Mainprize, D. R. Beniac, R. M. Cleverley, L. M. Cleverley, L. M. Gierasch, F. P. Ottensmeyer, and D. W. Andrews, The Structure of E. coli SRP Revealed by Scanning Transmission Electron Microscopy Suggests Interdomain Movement Is Involved in Signal Sequence Recognition, Mol. Cell Biol., 17, 5063-5074 (2006).

B.-R. Lin, L. M. Gierasch, C. Jiang, and P. C. Tai, Oocytes as an Electrophysiological Model System for Escherichia coli Protein Translocation, J. Membr. Biol., 214, 103-13 (2006).

B. Krishnan, A. Szymanska, and L. M. Gierasch, Site-Specific Fluorescent Labeling of Poly-Histidine Sequences Using Metal-Chelating Cysteine, Chem. Biol. & Drug Design, 69, 31-40 (2007).

Z. Ignatova, B. Krishnan, J. P. Bombardier, A. M. C. Marcelinio, J. Hong, and L. M. Gierasch, From the Test Tube to the Cell, Biopolymers-Peptide Science, 88, 157-163 (2007).
199. Z. Ignatova and L. M. Gierasch, Effects of Osmolytes on Protein Folding and Aggregation in Cells, Methods Enzymol., 428, 355-372 (2007).

J. F. Swain, G. Dinler, R. Sivendran, D. L. Montgomery, M. Stotz, and L. M. Gierasch, ATP-Induced Docking of Independent Domains in the Hsp70 Molecular Chaperone DnaK Is Reversed by Peptide Binding with an Intrinsic Role for the Interdomain Linker, Molecular Cell, 26, 27-39 (2007).

Z. Ignatova and L. M. Gierasch, A Method for Direct Measurement of Protein Stability In Vivo, Methods Mol. Biol., in press (2007).

Z. Ignatova and L. M. Gierasch, A Fluorescent Window into Protein Folding and Aggregation in Cells, Methods Cell Biol., in press (2007).

Z. Ignatova, A. K. Thakur, R. B. Wetzel, and L. M. Gierasch, In Vivo Aggregation of Polyglutamine Tracts Is a Multistep Process with Early Involvement of Flanking Sequences, submitted.