E. Roszmusz et al., Localization of disulfide bonds in the frizzled module of Ror1 receptor tyrosine kinase, J BIOL CHEM, 276(21), 2001, pp. 18485-18490
The frizzled (FRZ) module is a novel module type that was first identified
in G-protein-coupled receptors of the frizzled and smoothened families and
has since been shown to be present in several secreted frizzled-related pro
teins, in some modular proteases, in collagen XVIII, and in various recepto
r tyrosine kinases of the Bor family, The FRZ modules constitute the extrac
ellular ligand-binding region of frizzled receptors and are known to mediat
e signals of WNT family members through these receptors, With an eye toward
defining the structure of this important module family, we have expressed
the FRZ domain of rat Ror1 receptor tyrosine kinase in Pichia pastoris, By
proteolytic digestion and amino acid sequencing the disulfide bonds were fo
und to connect the 10 conserved cysteines in a 1-5, 2-4, 3-8, 6-10, and 7-9
pattern. Circular dichroism and differential scanning calorimetry studies
on the recombinant protein indicate that the disulfide-bonded FRZ module co
rresponds to a single, compact, and remarkably stable folding domain posses
sing both alpha -helices and beta -strands.