Effects Of Lys177Site Mutant On Unfolding And Refolding Of Human Brain-type Creatine Kinase

Single nucleotide polymorphism (SNP) is a common heritable mutation, whichis widely present in the human genome. Human brain-type creatine kinase (HBCK) isrelated with the ion transport pumps in brain. The neurodegenerative disorders areassociated with dysregulation of HBCK.K177R is a SNP of HBCK (rs36002620). In the present work, as compared towild-type HBCK, we investigated the effects of this mutation during unfolding andrefolding, including inactivation, exposure of mercapto groups and tyrosines, changesof intrinsic fluorescence, and renaturation in the absent and present of Dextran70andPEG2000. The novel findings included:1. Guanidine hydrochloride (GdnHCl) resulted in inactivation of WT andK177R in a dose-dependent manner, and K177R inactivation is similar to WT.2. Stability of K177R is worse than WT HBCK.3. K177R and WT in0-0.3M GdnHCl induced more compact structure.GdnHCl concentration is larger than0.3M, along with the increase of guanidineconcentration, more loose structure.4. Dextran70and PEG2000reduced the activity and rate of renaturation of WTand K177R. At the same concentration, the effects of PEG2000were worse than thoseof Dextran70during refolding, and the yields and rate of refolding were dependenton dilution ratio of WT and K177R.These findings highlight a theoretical mechanism for potential diseases inducedby HBCK SNP.