Kinetic properties of rat hepatic prolactin receptors |
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Authors: | B Rae-Venter T L Dao |
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Institution: | 1. Department of Breast Surgery, Roswell Park Memorial Institute, Buffalo, New York 14263 USA;2. Breast Cancer Research Unit, Roswell Park Memorial Institute, Buffalo, New York 14263 USA |
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Abstract: | Binding of 125I-labelled ovine prolactin to female rat liver membranes underequilibrium conditions showed an apparent Kd of 200 pM, and a Hill coefficient of 1.0. The association rate was second order, with a rate constant K1, of 2.1 × 107, 1.4 × 107, 1.2 × 107 and 4 × 106 M?1. min?1 at 37, 30, 24 and 4° respectively. At 24° there were two components to the dissociation; a faster phase with K?1=1.26 × 10?2. min?1 () and a slower phase with K?1=1.103 × 10?3. min?1. The apparent Kd (from K?1K1) was 1.05 nM for the faster phase and 87.5 pM for the slower phase. These data suggest that there is a conformational change following hormone binding which results in an increased receptor affinity, which effectively prevents release of bound hormone. |
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