βII L2079P Mutational Effect on Spectrin (αβ) 2 Tetramer Formation Natalie Palmer UIC REU 2010

Acknowledgements Professor Leslie Fung Andrea Antoniou, Ph.D. student Professors Takoudis and Jursich All REU members NIH NSF DOD EEC-NSF Grant # UIC REU 2010

Spectrin Cytoskeletal protein that gives stability to cells Brain spectrin plays a critical role in neuronal growth and secretion 2 α isoforms –αI, αII 5 β isoforms –βI, βII, βIII, βIV, βV UIC REU 2010

Organization UIC REU 2010

Project Description Site directed mutagenesis of  II. Mutation: L2079P In red blood cell  spectrin (  I), the corresponding residue is proline and the region downstream from the proline residue is unstructured. However, the region in brain  II appears to be helical. We propose that the mutation from Leu to Pro will result in a conformational change in  II and thus function differently. UIC REU 2010

Mutant Primer Design First Design A L E R L T T L E –WT: 5’ GCC CTG GAA AGG CTG ACT ACA TTG GAG 3’ A L E R P T T L E –MT: 5’ GCC CTG GAA AGG CCG ACT ACA TTG GAG 3’ Second Design A L E R L T T L E –WT: 5’ GCC CTG GAA AGG CTG ACT ACA TTG GAG 3’ A L E R P T T L E –MT: 5’ GCC CTG GAA AGG CCT ACT ACA TTG GAG 3’ StuI restriction site UIC REU 2010

Plasmid Preparation and Transformation Preparation –Polymerase Chain Reaction (PCR) Denature DNA Anneal primers to parent strand Extent primers –DpnI digestion Removes parent strand Plasmid analysis Transformation –Mutant DNA plasmid inserted into DH5α competent cells –Grow cells UIC REU 2010

Plasmid DNA Analysis DNA gel electrophoresis –Agarose gel Send to RRC for sequencing Analyze sequencing results UIC REU 2010

Transformation - BL21 Same as transformation to DH5α cells used for DNA analysis. BL21 competent cells are designed for optimal protein expression. Select colonies for “freeze down” to be used for high-density cell growth. UIC REU 2010

Whole Cell Electrophoresis UIC REU 2010 SDS-PAGE—buffers used in gel influence the electrophoretic mobility Proteins migrate on the gel depending on their size –Heavier migrates slower Low Molecular Weight standard used to calibrate protein migration on gel. IPTG added to induce protein expression kD LMWS 1 with IPTG 2 with IPTG 1 w/o IPTG 2 w/o IPTG LMWS

Protein Preparation Suspend cells with our protein in lysis buffer Sonicate cells to release proteins Centrifuge to remove pellet Load supernatant on affinity column to immobilize our protein (fused to GST) to column resin Elute our fusion protein (GST-  II L2079P) with GSH buffer UIC REU 2010

Purification Results βII L2079P LMWS Lysate Wash out Elution Profile Obtained 1 g of cells Collected fusion protein from column in fractions Plotted concentration vs. fraction number Ran polyacrylamide gel on fractions with highest concentrations 98% pure UIC REU 2010 kD

Preparation of αII-N3 αII-N3 is the binding partner of βII Prepared for use in isothermal titration calorimetry (ITC) Same preparation as βII L2079P UIC REU % pure LMWS Lysate Wash out kD

Preparation of βII WT Prepared for use in isothermal titration calorimetry (ITC) Same preparation as βII L2079P and αII LMWS Lysate kD Wash out 96% pure UIC REU 2010

Isothermal Titration Calorimetry (ITC) Schematic UIC REU UIC REU 2010

A + B   C K d = [C] / [A] [B] B is titrated into A, in large volume in isothermal cell. First titration point, all B introduced is associated with A. Heat of association is measured. At the end of the titration, B introduced is not associated with A and no heat released. ITC UIC REU 2010

ITC Continued ITC directly measures the binding affinity, binding stoichiometry, and change in enthalpy UIC REU 2010 Our Results [GST-αII 1-359] = 35 μM, 1.5 mL [GST-βII L2079P] = 2.1 μM, 7 μL per titration UIC REU 2010

Future Work Protein Analysis Do ITC experiments with protein samples and proper controls (WT) Determine K d values for βII L2079P with  II in the presence and absence of a inhibitory protein, rG5 or F11, using  II WT with  II as controls, to determine the effect of mutation on βII function UIC REU 2010

What I learned Research is a trial and error process; it can be frustrating when something goes wrong, but you have to work through the problems and when you get it right it is a very rewarding experience

Questions? UIC REU 2010