Wrightia tinctoria globulin (WTG), one of the major seed storage proteins, was isolated for the first time from
seeds of the medicinal plant. WTG was extracted and purified to homogeneity in two steps using anion-exchange and
size-exclusion chromatographies. On an SDS–PAGE gel under non-reducing conditions, a major band of ~56 kDa was
observed; under reducing conditions, however, two major polypeptides, one with molecular weight ~32-34 kDa and the
other with molecular weight ~22-26 kDa were observed. Intact mass determination by MALDI-TOF supported this observation.
The N-terminal amino acid sequence of WTG matched in NCBI database with an expressed sequence tag obtained
from the c-DNA of developing embryo m-RNA of Wrightia tinctoria. The EST sequence was further substantiated by partial
de novo internal sequencing using MALDI-TOF/TOF. The high sequence homology with seed storage protein 11S
globulin confirmed that WTG is a type of 11S globulin. Circular dichroism analysis showed that the secondary structure
of WTG consists predominantly of β-sheets (44.2%) and moderate content of α-helices (10.3%). WTG showed hemagglutinating
property indicating that the protein may possess lectin-like activity. WTG was crystallized at 20 °C by the vapour
diffusion method using PEG 400 as precipitant. The crystals belonged to the orthorhombic space group P212121 with cell
dimensions of a=109.9Å, b=113.2Å and c=202.2Å with six molecules per asymmetric unit. Diffraction data were collected
to a resolution of 2.2Å under cryocondition. Preliminary structure solution of WTG indicated the possibility of a
hexameric assembly in its asymmetric unit.