From the provided data please deduce one signal transduction mechanism through which PTH operates.

Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Since the age of 4, Mary , now aged 13, had suffered convulsions and muscle cramps
which responded to treatment with calcium salts and vitamin D. She had short and
stocky build with a number of skeletal abnormalities, especially metalcarpal and
metatarsal shortening and poor tooth development. On X-ray examination,
however, the bone density was found to be normal, indicating proper mineralization
of bone. Mary also had a marked reduction in her sense of smell. Her serum calcium
and phosphate level before and after administration of 1,25-D-dihydroxy vitamin D3
was as indicated in Table 1; there was little calcium in the urine. The production of
parathyroid hormone (PTH) was then measured in the patient before and after an
infusion of Ca2+ to raise calcium levels to the normal range. The results are shown in
Table 2. The patient’s urinary excretion of cyclic AMP in response to infused PTH was
less than 10% of normal. The specific binding of radiolabelled PTH to renal
membranes was in the normal range. Mary’s plasma levels of thyroid stimulating
hormone (TSH) were also above normal, whereas her thyroid hormone levels were
at the lower end of the normal range.

1-From the provided data please deduce one signal transduction mechanism
through which PTH operates.

2-When membranes prepared from a sample of the patients’s erythrocytes were
treated with cholera toxin and radiolabelled NAD+, a single polypeptide of Mr
approximately 45.000 was radiolabelled but only to 40% of the level in
membranes from control subjects. What does the experiment with cholera toxin
indicate about the possible molecular defect in the patient?

Table 1
Normal range
Patient
Patient after
administration of
Vit D3
Calcium (mM)
2.1-2.7
1.1
2.6
Phosphate (mM)
0.7-1.4
2.8
1.3
Table 2
Normal range
Patient
Patient after Ca2+
infusion
Calcium (mM)
PTH (ng/mL))
2.1-2.7
1.8
2.9
<0.5
3.1
undetectable
Transcribed Image Text:Table 1 Normal range Patient Patient after administration of Vit D3 Calcium (mM) 2.1-2.7 1.1 2.6 Phosphate (mM) 0.7-1.4 2.8 1.3 Table 2 Normal range Patient Patient after Ca2+ infusion Calcium (mM) PTH (ng/mL)) 2.1-2.7 1.8 2.9 <0.5 3.1 undetectable
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