Biology subjects

Kodama, H. M.

Publications and source records attributed to Kodama, H. M..

3 recordsLinked to original sources

bioRxiv2026

Mutation-induced heterogeneity of the β7-β8 loop of the Staphylococcus aureus class A sortase leading to enhanced catalytic efficiency characterized by NMR and enzyme kinetics

Bacterial sortase enzymes are cysteine transpeptidases at the surface of Gram-positive bacteria that ligate substrates to the cell wall. In addition, these enzymes are powerful tools in protein engineering applications via sortase-mediated ligation (SML) due to their covalent attachment of two substrates, with one containing a pentapeptide recognition motif with sequence LPXTG, where X=any amino acid, and the second, an N-terminal glycine. The class A sortase from Staphylococcus aureus (saSrtA) was the first to be identified, and over 25 years later, the most widely used SML variants continue to be derivatives of a directed-evolution-identified pentamutant of saSrtA, or saSrtA5M. We previously characterized P94, a position mutated in saSrtA5M that interacts directly with a structurally conserved loop (the {beta}7-{beta}8 loop) near the active site of wild-type saSrtA only in the inactive conformation. This work revealed that the single P94X mutation dramatically affects relative saSrtA activity, as well as specificity for the P2 (or X) position in the LPXTG recognition motif. This is largely driven by Km effects. Here, we further interrogated P94 by probing structural changes in the active, apo state of saSrtA in the presence of the P94D mutation, as well as via mutations in Y187, the {beta}7-{beta}8 loop residue hypothesized to interact directly with P94. The saSrtA enzyme is allosterically activated by calcium; therefore, we were interested if P94D would induce structural changes in the calcium-bound apo enzyme. We used 1H-15N NMR experiments to compare spectra between enzymatically inactive variants of saSrtA with and without the P94D mutation. We also used NMR to calculate relative binding affinities for a pentapeptide substrate to these variants, as well as enzymatically inactive saSrtA5M. Our NMR data, in combination with enzymatic assays using active variants confirmed differences in the active, apo states of these enzymes. Overall, this work provides additional atomic detail regarding the importance of the P94 residue in saSrtA substrate recognition.

biochemistry↗

bioRxiv2021

Structural and biochemical analyses of selectivity determinants in chimeric Streptococcus Class A sortase enzymes

Sequence variation in related proteins is an important characteristic that modulates activity and selectivity. An example of a protein family with a large degree of sequence variation is that of bacterial sortases, which are cysteine transpeptidases on the surface of gram-positive bacteria. Class A sortases are responsible for attachment of diverse proteins to the cell wall to facilitate environmental adaption and interaction. These enzymes are also used in protein engineering applications for sortase-mediated ligations (SML) or sortagging of protein targets. We previously investigated SrtA from Streptococcus pneumoniae, identifying a number of putative {beta}7-{beta}8 loop-mediated interactions that affected in vitro enzyme function. We identified residues that contributed to the ability of S. pneumoniae SrtA to recognize several amino acids at the P1 position of the substrate motif, underlined in LPXTG, in contrast to the strict P1 Gly recognition of SrtA from Staphylococcus aureus. However, motivated by the lack of a structural model for the active, monomeric form of S. pneumoniae SrtA, here, we expanded our studies to other Streptococcus SrtA proteins. We solved the first monomeric structure of S. agalactiae SrtA which includes the C-terminus, and three others of {beta}7-{beta}8 loop chimeras from S. pyogenes and S. agalactiae SrtA. These structures and accompanying biochemical data support our previously identified {beta}7-{beta}8 loop-mediated interactions and provide additional insight into their role in Class A sortase substrate selectivity. We argue that a greater understanding of individual SrtA sequence and structural determinants of target selectivity can facilitate the design or discovery of improved sortagging tools.

biochemistry↗

bioRxiv2021

A second specificity-determining loop in Class A sortases: Biochemical characterization of natural sequence variation in chimeric SrtA enzymes

Gram-positive bacteria contain sortase enzymes on their cell surfaces that catalyze transpeptidation reactions critical for proper cellular function. In vitro, sortases are used in sortase-mediated ligation (SML) reactions for a variety of protein engineering applications. Historically, sortase A from Staphylococcus aureus (saSrtA) has been the enzyme of choice for SML reactions. However, the stringent specificity of saSrtA for the sequence motif LPXTG limits its uses. Here, we use principal component analysis to identify a structurally conserved loop with a high degree of variability in all classes of sortases. We investigate the contribution of this {beta}7-{beta}8 loop, located between the catalytic cysteine and arginine residues and immediately adjacent to the target binding cleft, by designing and testing chimeric sortase enzymes. Our chimeras utilize natural sequence variation of Class A sortases from 8 species engineered into the SrtA sequence from Streptococcus pneumoniae (spSrtA). While some of our chimeric enzymes mimic the activity and selectivity of the wild-type protein from which the loop sequence is derived (e.g., that of saSrtA), others result in chimeric spSrtA enzymes able to accommodate a range of residues in the final position of the substrate motif (LPXTX). Using mutagenesis, structural, and sequence analyses, we identify three interactions facilitated by {beta}7-{beta}8 loop residues that appear to be broadly characteristic of Class A sortase enzymes. These studies provide the foundation for a deeper understanding of sortase target selectivity and can expand the sortase toolbox for future SML applications.

biochemistry↗