CADMIUM AND LEAD INTERACTIONS WITH EF-HAND PROTEINS: AN INTRINSIC FLUORESCENCE STUDY

Abstract

Toxic metal exposure is an increasingly important issue that is impacting a growing population. Frequent exposure can lead to adverse health effects such as cognitive impairment in children, diabetes, and cardiovascular issues. Exposure can come from many different sources, including some spices, paint, and e-cigarettes. Metals such as lead (Pb) and cadmium (Cd) can mimic essential metals like calcium (Ca) due to their similar atomic radii. This presents a threat to biological systems as it allows Pb and Cd to bind in place of Ca on protein active sites. Explored in this project, is the protein human cardiac troponin C (hcTnC), which is a Ca2+ binding protein that assists in contractions of cardiac muscles. Protein function could be altered if Pb or Cd bind in place of Ca, potentially leading to life-threatening cardiac events. Understanding the molecular mechanisms occurring during the interruption of Ca signaling pathways will lead to greater understanding of toxic metals and may lead to therapeutic methods intended to prevent these harmful effects. This study is focused on the N-terminal domain of hcTnC (NTD), and the impact metal binding has on protein structure. Specifically, the intrinsic fluorescence of tyrosine (excitation 280nm, emission 330nm) and phenylalanine (excitation 250nm, emission 280nm) residues were monitored in the apo and Ca(II), Zn(II), Pb(II), and Cd(II) bound states of NTD. Emission scans were obtained for apo, and metal bound protein samples. Emission scans for both did not reveal a significant change in fluorescent intensity. While previous data in the Spuches lab does indicate that metal binding occurs, these data reveal that binding does not result in a large structural change. Future studies will focus on potential functional change of the protein.