Chemistry and Biochemistry

Karin Crowhurst

Photo of Dr Karin Crowhurst
(818) 677-4288
Office location:
3109 Citrus Hall



Ph.D. (Biochemistry), University of Toronto
M.Sc. (Chemistry), University of Toronto 
B.Sc. Honours (Chemistry), Queen's University


California Institute of Technology, 2003-2006


Chemistry 100, Principles of Chemistry
Chemistry 365, Introduction to Biochemistry
Chemistry 461, Biochemistry I
Chemistry 461L, Biochemistry I Laboratory
Chemistry 462, Biochemistry II
Chemistry 462L, Biochemistry II laboratory
Chemistry 464, Principles of Biochemistry
Chemistry 464L, Principles of Biochemistry Laboratory
Chemistry 465, Topics in Biochemistry
Chemistry 567 and 595P, Investigating Protein Structure and Function
Chemistry 567L, Investigating Protein Structure and Function Laboratory


Dr. Crowhurst’s research is focused generally on using multidimensional, multinuclear NMR spectroscopy to to study the roles of structure, biophysical properties and protein dynamics on the specificity of protein-protein interactions in signal transmission, as well as the activities of disordered proteins. The lab is currently pursuing two major projects:

1. The role of internal motions in the specificity and affinity of RGS proteins for their Gα signaling partners. Members of the RGS protein family are responsible for deactivating G protein signaling. Ultimately, RGS proteins control the relay of signals that are triggered by light, smell, hormones or neurotransmitters. The lab’s primary goal is to better understand how RGS proteins are selective for particular Gα targets, despite having very similar binding sites, and how this influences signal transmission. Since these proteins are critical for the initiation or regulation of signaling cascades, answers to these questions may lead to improved understanding of the mechanisms that cause conditions such as cancer, schizophrenia and  neurodegenerative diseases, and can aid in drug design.

2. In vitro and in-cell investigation of the acid-stress chaperone HdeA. The stomach is an important barricade that helps to kill many bacteria before they can cause illness, in part by using its acidity to inactivate bacterial proteins. Some bacteria contain a small chaperone protein called HdeA that helps protect other proteins from becoming permanently inactivated and therefore helps bacteria survive and cause infection. Biophysical studies have provided clues that HdeA unfolds below pH 3.0 and interacts with its binding partners via hydrophobic interactions. However, there is a lack of data that monitors, in detail, the mechanism of unfolding and activation, both in vitro and in cells. Insight we gain may aid future development of vaccines or therapeutics that combat dysentery.

The protein NMR spectroscopic techniques used to address these biological questions are sophisticated and provide significantly more information on the structural and dynamic properties of proteins than can be obtained from standard one-dimensional 1H or 13C spectra.

Students joining the lab will have the opportunity to expand their understanding of the mechanism and biophysical properties of proteins at a detailed, molecular level. In addition, they can gain experience in expressing and purifying isotopically labeled proteins, in running multidimensional NMR experiments, and in using specialized computer software to analyze the collected data and obtain information about protein structure and motions.

REPRESENTATIVE PUBLICATIONS (* indicates student co-author)

  1. Aguirre-Cardenas, M.I.*, Geddes-Buehre, D.H.*, Crowhurst, K.A. (2021) "Removal of disulfide from acid stress chaperone HdeA does not wholly eliminate structure or function at low pH." Biochemistry and Biophysics Reports 27, 101064. DOI: 10.1016/j.bbrep.2021.101064 
  2. Widjaja, M.A.*, Gomez, J.S.*, Benson, J.M.* and Crowhurst, K.A. (2021) "Detection of key sites of dimer dissociation and unfolding initiation during activation of acid-stress chaperone HdeA at low pH." Biochimica et Biophysica Acta Proteins and Proteomics 1869, 140576. DOI: 10.1016/j.bbapap.2020.140576
  3. Pacheco, S.*, Widjaja, M.A.*, Gomez, J.S.*, Crowhurst, K.A. and Abrol, R. (2020) "The complex role of the N-terminus and acidic residues of HdeA as pH-dependent switches in its chaperone function" Biophysical Chemistry, 264, 106406. DOI: 10.1016/j.bpc.2020.106406
  4. Crowhurst, K. A., Horn, J. V. C.* and Weers, P. M. M. (2016) "Backbone and side chain chemical shift assignments of apolipophorin III from Galleria mellonella" Biomolecular NMR Assignments, 10(1), 143-147. DOI: 10.1007/s12104-015-9654-7
  5. Crowhurst, K. A. (2014) "13C, 15N and 1H backbone and side chain chemical shift assignment of acid-stress bacterial chaperone HdeA at pH 6” Biomolecular NMR Assignments, 8(2), 319-323. DOI: 10.1007/s12104-013-9508-0
  6. Garrison, M. A.* and Crowhurst, K. A. (2014) "NMR-monitored titration of acid-stress bacterial chaperone HdeA reveals that Asp and Glu charge neutralization produces a loosened dimer structure in preparation for protein unfolding and chaperone activation” Protein Science, 23(2), 167-178. DOI: 10.1002/pro.2402 
  7. Maly, J.* and Crowhurst, K. A. (2012) "Expression, purification and preliminary NMR characterization of isotopically labeled wild-type human heterotrimeric G protein α(i1)” Protein Expression and Purification, 84(2), 255-264. DOI: 10.1016/j.pep.2012.06.003
  8. Crowhurst, K. A. and Mayo, S. L. (2008) "NMR-detected conformational exchange observed in a computationally designed variant of protein Gβ1” Protein Engineering, Design and Selection 21(9), 577-587. DOI: 10.1093/protein/gzn035
  9. Shah, P. S., Hom, G. K., Ross, S. A., Lassila, J. K., Crowhurst, K. A. and Mayo, S. L. (2007) “Full-sequence computational design and solution structure of a thermostable protein variant,” Journal of Molecular Biology 372(1), 1-6. DOI: 10.1016/j.jmb.2007.06.032
  10. Neale, C., Marsh, J. A., Jack, F. E., Choy, W.-Y., Lee, A., Crowhurst, K. A. and Forman-Kay, J. D. (2007) “Improved structural characterization of the drkN SH3 domain unfolded state suggest a compact ensemble with native-like and non-native structure” Journal of Molecular Biology 367(5), 1494-1510. DOI: 10.1016/j.jmb.2007.01.038
  11. Crowhurst, K. A. and Forman-Kay, J. D. (2003) “Aromatic and methyl NOEs point to hydrophobic clustering in the unfolded state of an SH3 domain” Biochemistry-US 42(29), 8687-8695. DOI: 10.1021/bi034601p
  12. Crowhurst, K. A., Choy. W-Y., Mok, Y-K. and Forman-Kay, J. D. (2003) “Corrigendum to the paper by Mok et al. (1999) NOE data demonstrating a compact unfolded state for an SH3 domain under non-denaturing conditions” Journal of Molecular Biology 329(1), 185-187. DOI: 10.1016/S0022-2836(03)00400-5
  13. Tollinger, M., Crowhurst, K. A., Kay, L. E. and Forman-Kay, J. D. (2003) “Site-specific contributions to the pH dependence of protein stability” Proceedings of the National Academy of Sciences USA. 100(8), 4545-4550. DOI: 10.1073/pnas.0736600100
  14. Crowhurst, K. A., Tollinger, M. and Forman-Kay, J. D. (2002) “Cooperative interactions and a non-native buried Trp in the unfolded state of an SH3 domain” Journal of Molecular Biology. 322(1), 163-178. DOI: 10.1016/S0022-2836(02)00741-6
  15. Choy, W-Y., Mulder, F. A. A, Crowhurst, K. A., Muhandiram, D. R., Millett, I. S., Doniach, S., Forman-Kay, J. D. and Kay, L. E. (2002) “Distribution of molecular size within an unfolded state ensemble using small-angle X-ray scattering and pulse field gradient NMR techniques” Journal of Molecular Biology 316(1), 101-112. DOI: 10.1006/jmbi.2001.5328
  16. Woolley, G.A., Biggin, P.C., Schultz, A., Lien, L., Jaikaran, D.C., Breed, J., Crowhurst, K., Sansom, M.S. (1997) "Intrinsic rectification of ion flux in alamethicin channels: studies with an alamethicin dimer" Biophysical Journal 73(2), 770-778. DOI: 10.1016/S0006-3495(97)78109-8


  • Jonathon Benson (MS Biochemistry 2020): Investigation of HdeA chaperone action with a native client protein
  • Dane Geddes-Buehre (MS Biochemistry 2020): Examination of HdeA mutants to better elucidate the mechanism of acid chaperone activation
  • Marlyn Widjaja (MS Biochemistry 2018): Structure and dynamics studies of the acid-stress chaperone HdeA to investigate its mechanism of activation
  • Akachai Surinarintr (MS Biochemistry 2017): Investigation of internal motions in TrkB-d5 provides insight into molecular recognition and allostery
  • Shayla Brooks (MS Biochemistry 2016): Using NMR to probe the role of protein dynamics in interactions between G alpha (i1) and its regulator RGS4
  • Jan Maly (MS Biochemistry 2013): The integral role of the SUMO fusion protein system in successful expression and purification of two difficult proteins for NMR studies
  • Keen Kim (MS Biochemistry 2013) Expression and purification trials of human brain-derived neurotrophic factor (hBDNF) and its cognate receptor, tropomyosin-related kinase B (hTrkB), to characterize their conformational dynamics by NMR spectroscopy
  • William H. Kim (MS Biochemistry 2012): Intermediate timescale exchange in apo TrkB receptor provides insight into the role of molecular motions in its binding selectivity for neurotrophin signaling proteins
  • Naveen Battala (MS Biochemistry 2011): Development of a protocol to prepare isotopically labeled human neurotrophin-4 (hNT-4) and preliminary characterization of the protein by NMR spectroscopy 
  • Tamara Vartanian (MS Biochemistry 2009): Development of a protocol to express and purify isotopically labelled human Brain Derived Neurotrophic Factor for NMR analysis