title: Thermal induced unfolding of human serum albumin isomers: assigning residual α helices to domain II.
abstract: In this study we have investigated the heat induced denaturation of HSA by utilizing spectroscopic approaches including fluorescence and circular dichroism. Thermal denaturation of N isomer (domains I-III remain intact), B isomer (loss of helical structure of interdomain contacts) and I state (domain II intact) was found to be co-operative processes while for F isomer domains unfold non-cooperatively. These finding pointed out that during N-F transition, HSA suffers more structural alterations which are not localized only to domain III. Loss of secondary structure in the temperature range 20-60 °C without effecting tertiary structure of N isomer of HSA is mainly due to loss in helical extensions connecting domain I to II and domain II to III. All the four thermally denatured states (60-96 °C) of HSA retained approximately 50% residual α-helical structures. Near-UV spectroscopy used as a probe for tertiary structure indicated that heat denatured states lost almost all of the tertiary contacts thereby forming molten globule like states. Furthermore, our results provide evidence that residual helical structures are mainly located in domain II.
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
authors: Basir
authors: B
authors: Ahmad
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
authors: Ghazala
authors: G
authors: Muteeb
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
authors: Parvez
authors: P
authors: Alam
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
authors: Ankita
authors: A
authors: Varshney
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
authors: Nida
authors: N
authors: Zaidi
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
authors: Mohd
authors: M
authors: Ishtikhar
authors: Laboratory of Immunology & Molecular Physiology, Zoology Department, Faculty of Science, Assiut University, 71516 Assiut, Egypt.
authors: Gamal
authors: G
authors: Badr
authors: Food Science and Nutrition Department, National Research Center, Dokki, Cairo, Egypt; Deanship of Scientific Research, King Saud University, Riyadh, Saudi Arabia.
authors: Mohamed H
authors: MH
authors: Mahmoud
authors: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India. Electronic address: rizwanhkhan@hotmail.com.
authors: Rizwan Hasan
authors: RH
authors: Khan
mesh_terms: D002942:Circular Dichroism; D006801:Humans; D007536:Isomerism; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D012709:Serum Albumin
keywords: Denaturation; Human serum albumin; Molten globule; Urea