Biology subjects

Hengge, A. C.

Publications and source records attributed to Hengge, A. C..

3 recordsLinked to original sources

bioRxiv2025

Conformational Dynamics and Catalytic Backups in a Hyper-Thermostable Engineered Archaeal Protein Tyrosine Phosphatase

Protein tyrosine phosphatases (PTPs) are a family of enzymes that play important roles in regulating cellular signaling pathways. The activity of these enzymes is regulated by the motion of a catalytic loop that places a critical conserved aspartic acid side chain into the active site for acid-base catalysis upon loop closure. These enzymes also have a conserved phosphate binding loop that is typically highly rigid and forms a well-defined anion binding nest. The intimate links between loop dynamics and chemistry in these enzymes make PTPs an excellent model system for understanding the role of loop dynamics in protein function and evolution. In this context, archaeal PTPs, which have evolved in extremophilic organisms, are highly understudied, despite their unusual biophysical properties. We present here an engineered chimeric PTP (ShufPTP) generated by shuffling the amino acid sequence of five extant hyperthermophilic archaeal PTPs. Despite ShufPTPs high sequence similarity to its natural counterparts, ShufPTP presents a suite of unique properties, including high flexibility of the phosphate binding P-loop, facile oxidation of the active site cysteine, mechanistic promiscuity, and most notably, hyperthermostability, with a denaturation temperature likely >130 {degrees}C (>8 {degrees}C higher than the highest recorded growth temperature of any archaeal strain). Our combined structural, biochemical, biophysical and computational analysis provides insight both into how small steps in evolutionary space can radically modulate the biophysical properties of an enzyme, and showcase the tremendous potential of archaeal enzymes for biotechnology, to generate novel enzymes capable of operating under extreme conditions. Table of Contents Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=68 SRC="FIGDIR/small/645524v3_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@186bfccorg.highwire.dtl.DTLVardef@19a265borg.highwire.dtl.DTLVardef@14c526corg.highwire.dtl.DTLVardef@1b75920_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Redefining the Limits of Functional Continuity in the Early Evolution of P-Loop NTPases

At the heart of many nucleoside triphosphatases is a conserved sequence motif that binds phosphate. A current model of early enzyme evolution proposes that this 6-8 residue motif could have sparked the emergence of the very first nucleoside triphosphatases - a striking example of evolutionary continuity from simple beginnings, if true. To test whether this provocative evolutionary model holds for the ancient and ubiquitous P-Loop NTPases, the properties of seven disembodied Walker A-derived peptides were extensively characterized by Hamiltonian replica exchange molecular dynamics simulations. Although dynamic flickers of nest-like conformations were observed, significant structural similarity between the situated peptide and its disembodied counterpart was not detected - even in the presence of orthophosphate or a nucleotide. Simulations suggest that phosphate binding is non-specific, with a slight preference for GTP over orthophosphate. Control peptides with the same amino acid composition but different sequences and situated conformations behaved similarly to the Walker A peptides with respect to conformational dynamics and phosphate binding, revealing no indication that the Walker A sequence is privileged as a disembodied peptide. We conclude that the evolutionary history of the P-Loop NTPase family is unlikely to have started with a disembodied Walker A peptide in an aqueous environment. The limits of evolutionary continuity for this protein family, and the environmental context within which it emerged, must be reconsidered. Finally, we argue that motifs such as the Walker A motif may represent incomplete or fragmentary molecular fossils - the true nature of which have been eroded by time. Significance StatementThe first proteins were undoubtedly small, but when did those seeds emerge, and what did they look like? It is widely believed that the Walker A P-loop motif is a seed for the emergence of phosphate binding proteins, snugly binding phosphate in a structurally conserved nest. We probe this hypothesis through detailed computational characterization of disembodied Walker A and control peptides, showing that any nest formation is transient, and phosphate binding is weak and non-specific. Thus, we do not find structural continuity represented in the conserved Walker A motif, and current models of early P-loop evolution require revision. Further, care is required when interpreting highly conserved sequence fragments more broadly, as these may merely represent eroded molecular fossils.

biophysics↗

bioRxiv2018

Transition State Interactions in a Promiscuous Enzyme: Sulfate and Phosphate Monoester Hydrolysis by Pseudomonas aeruginosa Arylsulfatase

Pseudomonas aeruginosa arylsulfatase (PAS) hydrolyses sulfate and, promiscuously, phosphate monoesters. Enzyme-catalyzed sulfate transfer is crucial to a wide variety of biological processes, but detailed studies of the mechanistic contributions to its catalysis are lacking. We present an investigation based on linear free energy relationships (LFERs) and kinetic isotope effects (KIEs) of PAS and active site mutants that suggest a key role for leaving group (LG) stabilization. In LFERs wild type PAS has a much less negative Br0nsted coefficient ({beta}leaving groupobs-Enz = -0.33) than the uncatalyzed reaction ({beta}leavingroupobs = -1.81). This situation is diminished when cationic active site groups are exchanged for alanine. The considerable degree of bond breaking during the TS is evidenced by an 18Obridge KIE of 1.0088. LFER and KIE data for several active site mutants point to leaving group stabilization by active-site lysine K375, in cooperation with histidine H211. 15N KIEs combined with an increased sensitivity to leaving group ability of the sulfatase activity in neat D2O ({Delta}{beta}leaving groupH-D = +0.06) suggest that the mechanism for S-Obridge bond fission shifts, with decreasing leaving group ability, from charge compensation via Lewis acid interactions towards direct proton donation. 18Ononbridge KIEs indicate that the TS for PAS-catalyzed sulfate monoester hydrolysis has a significantly more associative character compared to the uncatalyzed reaction, while PAS-catalyzed phosphate monoester hydrolysis does not show this shift. This difference in enzyme-catalyzed TSs appears to be the major factor favoring specificity toward sulfate over phosphate in this promiscuous hydrolase, since other features are either too similar (uncatalyzed TS) or inherently favor phosphate (charge).

biochemistry↗