Please cite this article in press as: M. Zaman, et al., Int. J. Biol. Macromol. (2017), http://dx.doi.org/10.1016/j.ijbiomac.2017.07.083 ARTICLE IN PRESS G Model BIOMAC-7891; No. of Pages 10 International Journal of Biological Macromolecules xxx (2017) xxx–xxx Contents lists available at ScienceDirect International Journal of Biological Macromolecules j ourna l h o mepa ge: www.elsevier.com/locate/ijbiomac Research Article Cysteine as a potential anti-amyloidogenic agent with protective ability against amyloid induced cytotoxicity Masihuz Zaman a , Syed Mohammad Zakariya a , Saima Nusrat a , Tajalli Ilm Chandel a,b,c , Syed Musthapa Meeran b , Mohammad Rehan Ajmal a , Parvez Alam a , Wahiduzzaman c , Rizwan Hasan Khan a,∗ a Molecular Biophysics and Biophysical Chemistry Group, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, 202002, India b Laboratory of Cancer Epigenetics, Division of Endocrinology, CSIR-Central Drug Research Institute, Lucknow, India c Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India a r t i c l e i n f o Article history: Received 12 June 2017 Received in revised form 12 July 2017 Accepted 12 July 2017 Available online xxx Keywords: Amyloids Cell cytotoxicity Inhibition ThT binding a b s t r a c t Protein aggregation and misfolding have been allied with numerous human disorders and thus inhibition of such occurrence has been center for intense research efforts against these diseases. Here, we inves- tigated anti-fibrillation activity of cysteine and its effect on kinetics of stem bromelain amyloid fibril formation. We established the anti-fibrillation and anti aggregation activities of cysteine by using mul- tiple approaches like turbidity measurements, dye binding assays (ThT and ANS) and structural changes were monitored by circular dichroism (CD) followed by electron microscopy. Our experimental study inferred that cysteine inhibits temperature induced fibrillation of protein in a concentration dependent way. In addition, MDA-MB-231 cell viability of pre-formed amyloid was increased in presence of cysteine as compared to the fibrils alone. Furthermore, dynamic light scattering studies of native, aggregated as well as incubated (amyloids in presence of cysteine) samples indicates that cysteine restores native like structures of stem bromelain. Isothermal titration calorimetric results revealed that hydrogen bonding between cysteine and stem bromelain plays a significant role during inhibition of stem bromelain aggre- gation. However, thiophilic interaction between thiol group of cysteine and aromatic amino acid residue of stem bromelain may also have noteworthy role in inhibition of amyloid formation. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Protein misfolding and their subsequent aggregation under var- ious conditions has been concerned in various neurodegenerative diseases such as Prion, Parkinson’s, Alzheimer’s and systemic amy- loidosis diseases [1–3]. Although, fibrillation is associated with the progress of a variety of debilitating neurological diseases, cytotox- icity appears to be linked through pre-fibrillar aggregated states of proteins and peptides. Cytotoxicity is due to permeabilization of cell membranes by pre-fibrillar aggregates that are known to elevate the cytosolic Ca 2+ in neurons [4]. Mobilizing action of Ca 2+ on amyloids oligomeric states includes several mechanisms such as direct interaction with membrane components, activation of ∗ Corresponding author at: Molecular Biophysics and Biophysical Chemistry Group, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, 202002, India. E-mail addresses: rizwanhkhan1@gmail.com, rizwanhkhan@hotmail.com (R.H. Khan). cell surface receptors coupled to Ca 2+ influx and direct interac- tion with membrane components followed by destabilization of the membrane structure [5]. In spite of the variation in the bio- chemical properties and amino acid sequence, almost every protein illustrate tendency towards aggregation under various altered sit- uation like extreme pH, temperature, ionic strength and presence of denaturants [6–9]. Among these, temperature and pH are most persistent aspect that affects the succession of protein aggrega- tion process [10,11]. This may be due unfolding of proteins along with exposure of hydrophobic patches at altered pH and elevated temperature [12]. Conversely, different protein possess different mechanism for misfolding and aggregation [13]. Using different groups of compounds and molecules, researcher develops several potential treatment strategies to avert and/or reverse the aggre- gation processes. Plant derivatives, drug molecules, polyphenols, amino acids, metal ions are some structurally unrelated compounds that have been proved to weaken the intermolecular interactions during inhibition of self assembly progression of proteins [14–17]. These compounds or additives might control the proteins stability http://dx.doi.org/10.1016/j.ijbiomac.2017.07.083 0141-8130/© 2017 Elsevier B.V. All rights reserved.