Purification and characterisation of survivin homologs
School of Biotechnology, University of Jammu
Dr. Shekhar C. Mande
Lab of Structural Biology, National Centre for Cell Sciences, Pune 411007
Human survivin is a 16.5 kDa i.e., 142 amino acid protein. It is a member of inhibitor of apoptosis
protein (IAP) family. It is mainly expressed during the G
M phase of the cell cycle and is hypothesized
to inhibit many apoptotic cascades. It is generally overexpressed in tumour cells.
1.1. Structure of survivin
The structure of human survivin consists of N-terminal Zn
- binding BIR (Baculovirus IAP Repeat)
domain which is linked to a 65 Å amphipathic C-terminal alpha-helix.
In the BIR domain, three stranded antiparallel β-sheets are present which are surrounded by four small
α-helices. In this BIR domain a Zn
ion is present which is tetrahedrally coordinated by Cys 57, Cys
60, His 77, and Cys 84 bridges the core β-sheet with α4 and α5 helices .
Survivin’s unique feature is the presence of a 65 Å long C-terminal helix, α6, residues 100–140. Both
hydrogen bonding and hydrophobic interactions stabilize and fixes the direction of helical cord
between the BIR domain and residues of α6.
Human survivin exists as a dimer when alone and forms a bow-tie shaped dimer between the two α6
helices and form an 110° angle approximately with a tip-to-tip interhelical distance of 111 Å. But when
it is alone .