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Limited proteolysis of coupling factor-latent ATPase from Mycobacterium phlei. Effects of different enzymes and
Abstract:
The activation of the coupling factor-latent ATPase enzyme by tryptic proteolysis may resemble the activation of many proenzymes by limited proteolysis. The beta (53 000 dalton) subunit of solubilized coupling factor-latent ATPase from Mycobacterium phlei was selectively lost in some trypsin-treated samples. Since a concomitant loss of ATPase activity was not observed, the beta subunit may not be essential for ATPase catalytic activity. Treatment of solubilized coupling factor with chymotrypsin rapidly produced an A'-type (61 000 dalton) species from the native alpha (64 000 dalton) subunits with partial activation of the APTase enzyme. Secondary chymotryptic cleavage yielded an A"-type (58 000 dalton) species and a less-active enzyme. Storage of fresh coupling factor samples at -20degreeC in the presence of 4 mM MgCl2 with several freeze-thaw cycles resulted in loss of ATPase activity without apparent change in alpha subunit structure. Storage at 4 degrees C in the presence or absence of MgCl2 both decreased ATPase activity and generated A'-type alpha subunit species. Since presence was suspected. The peptide bonds first cleaved by trypsin, chymotrypsin, and the unknown protease are all apparantly located within the same small segment of alpha subunit polypeptide chain.
Insights
Tryptic proteolysis activates coupling factor-latent ATPase, similar to proenzyme activation. The beta subunit
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Coupling factor-latent ATPase activation mechanisms are not fully understood.
- Limited proteolysis is a known method for activating proenzymes.
- Investigating the role of subunits and proteases in ATPase activity is crucial.
Purpose of the Study:
- To investigate the activation mechanism of coupling factor-latent ATPase from Mycobacterium phlei.
- To determine the role of the beta subunit in ATPase catalytic activity.
- To characterize the effects of different proteases (trypsin, chymotrypsin) and storage conditions on ATPase activity and subunit structure.
Main Methods:
- Enzyme purification and solubilization of coupling factor-latent ATPase.
- Limited proteolysis using trypsin and chymotrypsin.
- Analysis of subunit composition and molecular weight using SDS-PAGE.
- Assay of ATPase activity.
- Investigating the effects of different storage conditions (temperature, MgCl2) on enzyme stability and activity.
Main Results:
- Tryptic proteolysis activates coupling factor-latent ATPase, potentially mimicking proenzyme activation.
- Selective loss of the beta subunit during trypsin treatment did not affect ATPase activity, suggesting it's non-essential for catalysis.
- Chymotrypsin treatment generated modified alpha subunits (A'-type and A''-type) with altered ATPase activity.
- Storage conditions, particularly freeze-thaw cycles and 4°C storage with MgCl2, led to decreased ATPase activity and alpha subunit modification.
- Proteolytic cleavage sites for trypsin, chymotrypsin, and an unknown protease appear to be in the same region of the alpha subunit.
Conclusions:
- The beta subunit is likely not essential for the catalytic activity of Mycobacterium phlei coupling factor-latent ATPase.
- Proteolytic cleavage, particularly of the alpha subunit, plays a significant role in modulating ATPase activity.
- Enzyme stability is sensitive to storage conditions, with MgCl2 and temperature influencing activity and subunit integrity.