Undergraduate research in the McLaughlin Lab makes primary use of macromolecular x-ray crystallography, along with several biochemical & biophysical methods including fluorescence anisotropy, to investigate protein structure and function.
The McLaughlin Lab is an UNDERGRADUATE only lab. If you are a Lehigh undergraduate interested in working in our lab, please contact Dr. McLaughlin at krm514 for more information.
Please see my Lehigh faculty page for more information on our research.
(L) Steven presenting at the 2016 Biological Sciences Undergraduate Research Symposium. (R) His xtals of the wt and mutant!
Ryan presenting his work in the Miwa-McLaughlin Mountaintop Project at the end of Summer 2016.
Postdoctoral Research- Redinbo Group, UNC Chapel Hill
Structural and biochemical characterization of key conjugative plasmid transfer (CPT) protein-DNA interactions that may serve as potential drug targets. During CPT, genetic material is transmitted between bacterial cells in part by a complex of proteins called the relaxosome, conferring virulence factors and antibiotic resistance. Successful conjugative DNA transfer depends on key catalytic relaxosome components to nick one strand of the duplex DNA plasmid and separate the DNA strands while cell-to-cell transfer occurs. The TraI protein from the conjugative Salmonella plasmid pCU1 fulfills these key catalytic roles, as it contains both single-stranded DNA-nicking relaxase and ATP-dependent helicase domains within a single polypeptide. I unraveled the helicase determinants of Salmonella pCU1 TraI through DNA binding, ATPase, and DNA strand separation assays. Collectively, these data defined the helicase motifs of TraI and revealed a previously uncharacterized C-terminal functional domain that uncouples ATP hydrolysis from strand separation activity. My work characterizing the helicase function of TraI is published in the Journal of Bacteriology.
Doctoral Research- Kielkopf Group, University of Rochester
Protein-nucleic acid interactions are essential for gene expression. My thesis work focused on the structural and energetic basis of several protein-nucleic acid interactions: (1) To investigate the molecular mechanism for NADH/NAD+ sensing among Rex-family members we solved the crystal structures of Thermus aquaticus Rex (T-Rex) bound to (i) NAD+/DNA, (ii) DNA , and (iii) without ligand, revealing that binding of NADH releases Rex from the DNA site following a large conformational change. I also used circular dichroism and isothermal titration calorimetry to characterize a series of structure-based mutants, thereby establishing a key triad of residues sense the redox state of the bound NAD(H). This work is published in Molecular Cell. (2) Little is known concerning the thermodynamic basis for RNA recognition by RRMs, a highly prevalent class of RNA binding domain in human proteins. Using ITC, I characterized RNA binding by four distinct RRM-containing proteins. All four RRM-containing proteins exhibited remarkable large magnitudes for the enthalpy and the entropy changes during RNA binding. Site-specific mutations implicated conserved aromatic residues of the RRM as key contributors to this thermodynamic effect. This work is published in Biochemistry. (3) Purine interruptions of polypyrimidine (Py) tract splice site signals contribute to human genetic diseases. To understand how U2AF65 accommodates certain purine interruptions, we identified a preferred binding site of U2AF65for purine substitutions in the 3' regions of Py tracts. I helped solve two crystal structures of U2AF65 bound to either A- or G-containing Py tracts. Based on comparisons to other U2AF65 structures with previously identified pyrimidine-containing structures, a D231V U2AF65 mutant was created an crystallized, that would specify U over other nucleotides. The D231V amino acid change restored U2AF(65) affinity for multiple mutated splice sites tested that cause human genetic diseases.. This work was recently (2014) completed and published in PNAS.
Agrawal A., McLaughlin K.J., Jenkins J.L., Kielkopf C.L. “A Structure-Guided U2AF65 Variant Improves Recognition and Splicing of a Defective pre-mRNA.” Proc Natl Acad Sci U S A. 2014, 111(49):17420-5 Pubmed
McLaughlin K.J., Nash R.P., Redinbo M.R. “Unique Helicase Determinants in the essential conjugative factor TraI from Salmonella typhimurium plasmid pCU1.” J. Bacteriol. 2014, 196(17):3082-90 doi:10.1128/JB.01496-14 Pubmed
McLaughlin K.J., Jenkins J.L., Kielkopf C.L. “Large Favorable Enthalpy Changes Drive Specific RNA Recognition by RNA Recognition Motif Proteins.” Biochemistry 2011, 50(9):1429-31 Text/PDF
McLaughlin K.J., Strain-Damerell, C.M., Xie, K., Brekasis, D., Soares, A.S., Paget, M.S. and Kielkopf, C.L. Structural Basis for NADH/NAD+ Redox Sensing by a Rex-Family Repressor. Molecular Cell. 2010 May 28;38(4):563-75. Text/PDF
Buboltz JT, Bwalya C, Williams K, Schutzer M. “High-resolution mapping of phase behavior in a ternary lipid mixture: do lipid-raft phase boundaries depend on the sample preparation procedure?” Langmuir 2007, 23:11968-71. Text/PDF