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Studies on guinea-pig macrophage migration inhibitory factor (MIF). II. Purification of MIF after treatment with
Abstract:
Treatment of guinea-pig macrophage migration inhibitory factor (MIF) containing culture supernatants with the denaturing agents guanidine hydrochloride (Gu HCl) or urea, in the presence or absence of the reducing agent 2-mercaptoethanol (2-ME), or with sodium dodecyl sulphate (SDS), does not destroy biological activity. Alkylation of reduced MIF preparations results in a considerable decrease or total loss of MIF activity. Treatment of supernatants with the combinations, Gu HCl and 2-ME or urea and 2-ME results in the recovery of MIF activity in association with molecules less than 30,000 in molecular weight (mol. wt). After removal of the agents by dialysis, MIF activity is found associated with molecules larger than 30,000. The reduction in mol. wt is dependent on the presence of 2-ME. When MIF-containing supernatants are treated with urea and SDS and fractionated by preparative polyacrylamide gel electrophoresis (PAGE) in the presence of the same agents, MIF activity is recovered in the mol. wt range of 42,000--80,000. When supernatants are treated with 2-me, in addition to urea and SDS, and preparative PAGE is performed in their presence, MIF activity is found associated with material having a mol. wt of 15,000--18,000. Analytical SDS-PAGE of this fraction reveals two or three closely grouped bands corresponding to the above mol. wt range.
Insights
Guinea-pig macrophage migration inhibitory factor (MIF) retains activity after denaturation. Reducing agents like 2-mercaptoethanol (2-ME) are crucial for reducing MIF molecular weight and activity.
Area of Science:
- Immunology
- Protein Chemistry
Background:
- Macrophage migration inhibitory factor (MIF) is a key cytokine in immune responses.
- Understanding MIF's molecular properties is essential for developing targeted therapies.
Purpose of the Study:
- To investigate the effects of denaturing and reducing agents on guinea-pig MIF biological activity and molecular weight.
- To characterize the molecular behavior of MIF under various chemical treatments.
Main Methods:
- Treatment of MIF-containing supernatants with guanidine hydrochloride (Gu HCl), urea, 2-mercaptoethanol (2-ME), and sodium dodecyl sulphate (SDS).
- Analysis of biological activity and molecular weight (mol. wt) using dialysis and preparative polyacrylamide gel electrophoresis (PAGE).
- SDS-PAGE for detailed molecular characterization.
Main Results:
- MIF activity is resistant to Gu HCl, urea, and SDS alone.
- Reducing agents (2-ME) are necessary for reducing MIF's molecular weight and can lead to loss of activity upon alkylation.
- Treatment with urea and 2-ME yields MIF activity associated with molecules <30,000 Da, which revert to >30,000 Da after agent removal.
- Preparative PAGE in the presence of urea and SDS shows MIF activity between 42,000–80,000 Da, further reduced to 15,000–18,000 Da with the addition of 2-ME.
Conclusions:
- MIF's biological activity is stable under common denaturing conditions.
- The molecular weight and potentially the activity of MIF are modulated by reducing conditions, suggesting a role for disulfide bonds in its structure.
- These findings provide insights into MIF's quaternary structure and its behavior in different biochemical environments.
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