Honors & Awards
Postdoctoral fellowship, Hereditary Disease Foundation
Boards, Advisory Committees, Professional Organizations
Chair of the organizing committee, Biophysical Society Thematic Meeting: "Revisiting the Central Dogma at the Single Molecule Level" (2018 - 2019)
Licenciado, Universidad Peruana Cayetano Heredia (2011)
Bachelor of Science, Universidad Peruana Cayetano Heredia (2008)
Doctor of Philosophy, University of California Berkeley (2016)
Judith Frydman, Postdoctoral Faculty Sponsor
Knots can impair protein degradation by ATP-dependent proteases.
Proceedings of the National Academy of Sciences of the United States of America
2017; 114 (37): 9864–69
ATP-dependent proteases translocate proteins through a narrow pore for their controlled destruction. However, how a protein substrate containing a knotted topology affects this process remains unknown. Here, we characterized the effects of the trefoil-knotted protein MJ0366 from Methanocaldococcus jannaschii on the operation of the ClpXP protease from Escherichia coli ClpXP completely degrades MJ0366 when pulling from the C-terminal ssrA-tag. However, when a GFP moiety is appended to the N terminus of MJ0366, ClpXP releases intact GFP with a 47-residue tail. The extended length of this tail suggests that ClpXP tightens the trefoil knot against GFP, which prevents GFP unfolding. Interestingly, if the linker between the knot core of MJ0366 and GFP is longer than 36 residues, ClpXP tightens and translocates the knot before it reaches GFP, enabling the complete unfolding and degradation of the substrate. These observations suggest that a knot-induced stall during degradation of multidomain proteins by AAA proteases may constitute a novel mechanism to produce partially degraded products with potentially new functions.
View details for DOI 10.1073/pnas.1705916114
View details for PubMedID 28847957
View details for PubMedCentralID PMC5604015
Substrate-translocating loops regulate mechanochemical coupling and power production in AAA plus protease C1pXP
NATURE STRUCTURAL & MOLECULAR BIOLOGY
2016; 23 (11): 974-981
ATP-dependent proteases of the AAA+ family, including Escherichia coli ClpXP and the eukaryotic proteasome, contribute to maintenance of cellular proteostasis. ClpXP unfolds and translocates substrates into an internal degradation chamber, using cycles of alternating dwell and burst phases. The ClpX motor performs chemical transformations during the dwell and translocates the substrate in increments of 1-4 nm during the burst, but the processes occurring during these phases remain unknown. Here we characterized the complete mechanochemical cycle of ClpXP, showing that ADP release and ATP binding occur nonsequentially during the dwell, whereas ATP hydrolysis and phosphate release occur during the burst. The highly conserved translocating loops within the ClpX pore are optimized to maximize motor power generation, the coupling between chemical and mechanical tasks, and the efficiency of protein processing. Conformational resetting of these loops between consecutive bursts appears to determine ADP release from individual ATPase subunits and the overall duration of the motor's cycle.
View details for DOI 10.1038/nsmb.3298
View details for Web of Science ID 000386992700007
View details for PubMedID 27669037
New insights into the regulatory mechanisms of ppGpp and DksA on Escherichia coli RNA polymerase–promoter complex
Nucleic Acids Research
2015; 43 (10): 5249–5262
View details for DOI 10.1093/nar/gkv391
Protein denaturation at a single-molecule level: the effect of nonpolar environments and its implications on the unfolding mechanism by proteases.
2015; 7 (7): 2970–77
Most proteins are typically folded into predetermined three-dimensional structures in the aqueous cellular environment. However, proteins can be exposed to a nonpolar environment under certain conditions, such as inside the central cavity of chaperones and unfoldases during protein degradation. It remains unclear how folded proteins behave when moved from an aqueous solvent to a nonpolar one. Here, we employed single-molecule atomic force microscopy and molecular dynamics (MD) simulations to investigate the structural and mechanical variations of a polyprotein, I278, during the change from a polar to a nonpolar environment. We found that the polyprotein was unfolded into an unstructured polypeptide spontaneously when pulled into nonpolar solvents. This finding was corroborated by MD simulations where I27 was dragged from water into a nonpolar solvent, revealing details of the unfolding process at the water/nonpolar solvent interface. These results highlight the importance of water in maintaining folding stability, and provide insights into the response of folded proteins to local hydrophobic environments.
View details for DOI 10.1039/c4nr07140a
View details for PubMedID 25597693
The ClpXP Protease Unfolds Substrates Using a Constant Rate of Pulling but Different Gears
2013; 155 (3): 636-646
ATP-dependent proteases are vital to maintain cellular protein homeostasis. Here, we study the mechanisms of force generation and intersubunit coordination in the ClpXP protease from E. coli to understand how these machines couple ATP hydrolysis to mechanical protein unfolding. Single-molecule analyses reveal that phosphate release is the force-generating step in the ATP-hydrolysis cycle and that ClpXP translocates substrate polypeptides in bursts resulting from highly coordinated conformational changes in two to four ATPase subunits. ClpXP must use its maximum successive firing capacity of four subunits to unfold stable substrates like GFP. The average dwell duration between individual bursts of translocation is constant, regardless of the number of translocating subunits, implying that ClpXP operates with constant "rpm" but uses different "gears."
View details for DOI 10.1016/j.cell.2013.09.022
View details for Web of Science ID 000326571800017
View details for PubMedID 24243020