Using model proteins to quantify the effects of pathogenic mutations in Ig-like proteins.
It has proved impossible to purify some proteins implicated in disease in sufficient quantities to allow a biophysical characterization of the effect of pathogenic mutations. To overcome this problem we have analyzed 37 different disease-causing mutations located in the L1 and IL2Rgamma proteins in well characterized related model proteins in which mutations that are identical or equivalent to pathogenic mutations were introduced. We show that data from these models are consistent and that changes in stability observed can be correlated to severity of disease, to correct trafficking within the cell and to in vitro ligand binding studies. Interestingly, we find that any mutations that cause a loss of stability of more than 2 kcal/mol are severely debilitating, even though some model proteins with these mutations can be easily expressed and analyzed. Furthermore we show that the severity of mutation can be predicted by a DeltaDeltaG(evolution) scale, a measure of conservation. Our results demonstrate that model proteins can be used to analyze disease-causing mutations when wild-type proteins are not stable enough to carry mutations for biophysical analysis.
Randles
Lucy G
LG
University of Cambridge, Department of Chemistry, Medical Research Council Centre for Protein Engineering, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Lappalainen
Ilkka
I
Fowler
Susan B
SB
Moore
Benjamin
B
Hamill
Stefan J
SJ
Clarke
Jane
J
D020022:Genetic Predisposition to Disease; D006801:Humans; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D053631:Interleukin Receptor Common gamma Subunit; D008958:Models, Molecular; D009154:Mutation; D039842:Neural Cell Adhesion Molecule L1 / Q000737:chemistry* / Q000235:genetics; D011237:Predictive Value of Tests; D017434:Protein Structure, Tertiary; D018123:Receptors, Interleukin / Q000737:chemistry* / Q000235:genetics; D017421:Sequence Analysis; D013329:Structure-Activity Relationship
C507941:IL2RG protein, human; D007136:Immunoglobulins; D053631:Interleukin Receptor Common gamma Subunit; D039842:Neural Cell Adhesion Molecule L1; D018123:Receptors, Interleukin