Biennial Report 2011–2012

Department of Bioinformatics
signaling response triggered upon binding to the hormone
receptor. Another mutant (Pro73Arg) showed an increased
propensity towards alternative conformation, but no visible
effect on its biological activity. Computational analysis of the
third mutation (Arg8Trp) did not reveal any significant alterations
in the assembly of intact hCG as also confirmed by
experiments. In summary, the study suggested that only mutations
with neutral or mild functional consequences might
be tolerated in the major hCGβ coding genes, CGB5 and
CGB8. Results of the study [6] were reported as a cover story
in “Molecular Human Reproduction” (Fig. 6).
Figure 5. Correlation between high electrostatic potential and the nonring
architecture of DNA sliding clamps. Yeast PCNA has a closed ring,
human cytomegalovirus UL44 is an open dimer. Human Hus1 is part
of the ring-shaped 9-1-1 complex, but perhaps may also bind DNA as a
monomer.
Analysis of rare missense mutations of human
chorionic gonadotrophin (hCG) β-subunit
In collaboration with Prof. Maris Laan (University of Tartu,
Estonia) we explored the impact of several rare missense mutations
of human chorionic gonadotrophin (hCG) β-subunit.
Placental hCG is one of the key hormones determining success
of early pregnancy. Like other heterodimeric glycoprotein
hormones (luteinizing hormone, follicle-stimulating
hormone and thyroid-stimulating hormone), hCG is formed
by non-covalent association of the common α-subunit and
the hormone-specific β-subunit. During previous survey of
over a thousand of North-Europeans, three rare mutations
(Val56Leu, Arg8Trp and Pro73Arg) within hCG β-subunit
were identified. Using combination of computational (sequence
and structure analysis, molecular dynamics) and experimental
(co-immunoprecipitation, immuno- and bioassays)
approaches we assessed the impact of these mutations
on the structure and function of hCG. In computational assessment
the Val56Leu mutation displayed the most dramatic
impact on the assembly of the intact hCG. This finding
was confirmed by experiments showing that compared to the
wild-type only about 10% of the mutant hCGβ assembled
into secreted intact hCG. However, interestingly, the effect
of poor dimerization was compensated by a much stronger
Figure 6. The MHR cover displaying the hCG structure with three
residues affected by the identified mutations shown in the space-filling
representation.
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