The Journal of biological chemistry
-
Proline porter II is rapidly activated when nongrowing bacteria are subjected to a hyperosmotic shift (Grothe, S., Krogsrud, R. L., McClellan, D. J., Milner, J. ⋯ Proline porter II was activated by NaCl and sucrose with a half-time of approximately 1 min in both whole cells and membrane vesicles. Thus, activation of proline porter II was reversible. It occurred at a rate comparable to that of K+ influx and much more rapid than the genetic regulatory responses that follow a hyperosmotic shift.
-
The catabolic system, translocating then beta-oxidizing fatty acids in the mitochondria and considered as the major energy generator in the heart, was shown in the present study to be strongly regulated by fatty acid-binding protein (FABP), a self-aggregated and exclusive protein for the binding and transport of fatty acids in the cardiac cell cytoplasm. The mechanism behind this regulation was investigated by using new techniques in this field: i.e. electron spin resonance (ESR) and spin-labeling for the simultaneous analysis of partitioning and beta-oxidation of fatty acids in the isolated cardiac mitochondria. ⋯ Two of the multi-self-aggregated FABP molecular species, namely those existing at FABP concentrations around 1.1 and 2.2 g.liter-1, were found to act as specific translocators delivering acylcarnitine to the mitochondrial beta-oxidative system. The energy production in the heart might thus be critically dependent on optimized FABP concentrations in the cardiac cells.