Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The DNA-binding form of the calf uterine androgen receptor (AR) was subjected to limited protease digestion using chymotrypsin, trypsin and a rat prostate cytosol protease. The properties of the generated polypeptide fragments were identified and compared with those of the intact AR. Physicochemical characterization was achieved through sedimentation analysis, gel filtration chromatography and DEAE anion exchange chromatography. Intactness of functional binding domains was evaluated by measuring the retention of steroid- and DNA-binding capacity. Under non-denaturing conditions the intact AR is a highly asymmetrical molecule with a Stokes radius (RS) of 45A, a sedimentation coefficient of 4.3S and a relative molecular mass of 80,000 daltons. This form of AR has an intrinsic binding affinity for DNA and was eluted from DNA-cellulose with 9 mM MgCl2. Chymotrypsin produced a more globular polypeptide (RS: 31A; 3.1S; 41,000 daltons) with a decreased net negative charge. This fragment also displayed DNA-binding affinity but required a higher concentration of MgCl2 (14 mM) for DNA-cellulose elution, indicating an increased affinity for DNA. The observed reduction in molecular size upon chymotrypsin treatment was confirmed when analysed by SDS-polyacrylamide gel electrophoresis after covalently labelling of the AR with [3H]R1881. Rat prostate cytosol contains a protease which is very active in generating an AR polypeptide with an increased affinity for DNA, without changing the AR net negative charge (RS: 33A; 3.7S; 51,000 daltons). The specificity of this protease remained unknown since none of a large number of inhibitors was able to inactivate this enzyme. The fragment generated is different from that obtained with chymotrypsin since significant differences in size as well as in charge were measured. Trypsin treatment generated a much smaller polypeptide (RS: 25A; 2.9S; 30,000 daltons) which had lost its DNA-binding capacity, but not its steroid binding site. This form probably represents the so-called meroreceptor. When intact AR was treated sequentially with prostate cytosol and trypsin, a polypeptide fragment with identical properties was obtained, indicating the spatial separation of two of the proteolytic cleavage sites. These studies provide evidence for the distinct nature of the molecular domains for androgen and DNA interaction on the calf uterine AR.
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PMID:Analysis of steroid- and DNA-binding domains of the calf uterine androgen receptor by limited proteolysis. 330 38

The changes in the bending pattern of flagella induced by an increased intracellular Ca(2+) concentration are caused by changes in the pattern and velocity of microtubule sliding. However, the mechanism by which Ca(2+) regulates microtubule sliding in flagella has been unclear. To elucidate it, we studied the effects of Ca(2+) on microtubule sliding in reactivated sea urchin sperm flagella that were beating under imposed head vibration. We found that the maximum microtubule sliding velocity obtainable by imposed vibration, which was about 170-180 rad/second in the presence of 250 microM MgATP and <10(-9) M Ca(2+), was decreased by 10(-6)-10(-5) M Ca(2+) by about 15-20%. Similar decrease of the sliding velocity was observed at 54 and 27 microM MgATP. The Ca(2+)-induced decrease of the sliding velocity was due mainly to a decrease in the reverse bend angle. When the plane of beat was artificially rotated by rotating the plane of vibration of the pipette that held the sperm head, the asymmetric bending pattern also rotated at 10(-5) M Ca(2+) as well as at <10(-9) M Ca(2+). The rotation of the bending pattern was observed at MgATP higher than 54 microM ( approximately 100 microM ATP). These results indicate that the Ca(2+)-induced decrease of the sliding velocity is mediated by a rotatable component or components (probably the central pair) at high MgATP, but is not due to specific dynein arms on particular doublets. We further investigated the effects of a mild trypsin treatment and of trifluoperazine on the Ca(2+)-induced decrease in sliding velocity. Axonemes treated for 3 minutes with a low concentration (0.1 microgram/ml) of trypsin beat with a more symmetrical waveform than before the treatment. Also, their microtubule sliding velocity and reverse bend angle were not affected by high Ca(2+) concentrations. Trifluoperazine (25-50 microM) had no effect on the decrease of the sliding velocity in beating flagella at 10(-5) M Ca(2+). However, the flagella that had been 'quiescent' at 10(-4) M Ca(2+) resumed asymmetrical beating following an application of 10-50 microM trifluoperazine. In such beating flagella, both the sliding velocity and the reverse bend angle were close to their respective values at 10(-5) M Ca(2+). Trypsin treatment induced a similar recovery of beating in quiescent flagella at 10(-)(4) M Ca(2+), albeit with a more symmetrical waveform. These results provide first evidence that, at least at ATP concentrations higher than approximately 100 microM, 10(-6)-10(-5) M Ca(2+) decreases the maximum sliding velocity of microtubules in beating flagella through a trypsin-sensitive regulatory mechanism which possibly involves the central pair apparatus. They also suggest that calmodulin may be associated with the mechanism underlying flagellar quiescence induced by 10(-4) M Ca(2+).
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PMID:Calcium regulation of microtubule sliding in reactivated sea urchin sperm flagella. 1067 72