To obtain more insight into the mechanisms regulating @entity93 : @entity2945 cytidylyltransferase (CT), we determined the effect of @entity3952 treatment on the rate of CT release from permeabilized Hep G2 cells and the distribution of the CT remaining in the permeabilized cells. When we permeabilized untreated cells in pH 7.5 buffer containing 0.15 M @entity4338 , the rate of CT release was much slower than the release of @entity880 dehydrogenase. @entity3952 treatment caused a further decrease in CT release from cells. In untreated cells, 70-80% of the CT remaining in cells 10 min after permeabilization was recovered as soluble CT. @entity3952 treatment increased the amount of bound CT but over 50% of the CT in cells 10 min after permeabilization was recovered as soluble CT. In both control and @entity3952 -treated cells, the increase in CT release with time correlated with a decrease in the amount of CT recovered from permeabilized cells as soluble CT. These results suggested that CT existed in a form that was not immediately available for release from permeabilized cells, but was recovered in the soluble fraction after cell disruption. When cells were permeabilized in 10 mM @entity8304 -20% @entity653 -5 mM @entity1025 pH 6.5, over 80% of CT in control and over 90% of CT in @entity3952 -treated cells was recovered bound to the particulate fraction. Essentially no CT was released from the cells. The recovery of CT in the particulate fraction required @entity1025 to be present when permeabilization was initiated. The addition of @entity1025 , after cells were disrupted, did not increase CT in the particulate fraction. In untreated cells, 50% of bound CT was active. @entity3952 treatment increased the amount of active CT in the particulate fraction to over 70% of total. About 50% of particulate CT in untreated cells but only 15% in @entity3952 -treated cells was extracted with 0.15 M @entity4338 . Inactive CT was preferentially extracted by @entity4338 . The bound CT was recovered in isolated nuclei. Overall, the results suggested that both inactive and active CT are bound to nuclear membranes, and that the activation of CT involves conversion of CT loosely bound to membrane to a form more tightly bound to membranes perhaps by hydrophobic interaction with phospholipids. This model does not involve translocation from a soluble pool.

Studies on the regulation of XXXX : @entity2945 cytidylyltransferase using permeabilized HEP G2 cells: evidence that both active and inactive enzyme are membrane-bound.

@entity3952 :: ('MESH:D019301', 'Chemical') :: ['Oleate', 'oleate'] @entity1025 :: ('CHEBI:18420', 'Chemical') :: ['Mg2+'] @entity93 :: ('MESH:D003570', 'Chemical') :: ['CTP'] @entity8304 :: ('MESH:C029899', 'Chemical') :: ['imidazole'] @entity653 :: ('MESH:D005990', 'Chemical') :: ['glycerol'] @entity880 :: ('MESH:D019344', 'Chemical') :: ['lactate'] @entity2945 :: ('MESH:D010767', 'Chemical') :: ['phosphocholine'] @entity4338 :: ('CHEBI:32588', 'Chemical') :: ['KCl']
@entity93 :: (MESH:D003570,Chemical) :: ['CTP']
