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The identification and characterization of IbpA, a novel α-crystallin-type heat shock protein from mycoplasma
Innokentii E Vishnyakov1, Sergei A Levitskii, Valentin A Manuvera
1Institute of Cytology, Russian Academy of Sciences, Saint Petersburg 194064, Russia.
Abstract:
α-Crystallin-type small heat shock proteins (sHsps) are expressed in many bacteria, animals, plants, and archaea. Among mycoplasmas (Mollicutes), predicted sHsp homologues so far were found only in the Acholeplasmataceae family. In this report, we describe the cloning and functional characterization of a novel sHsp orthologue, IbpA protein, present in Acholeplasma laidlawii. Importantly, similar to the endogenously expressed sHsp proteins, the recombinant IbpA protein was able to spontaneously generate oligomers in vitro and to rescue chemically denatured bovine insulin from irreversible denaturation and aggregation. Collectively, these data suggest that IbpA is a bona fide member of the sHsps family. The immune-electron microscopy data using specific antibodies against IbpA have revealed different intracellular localization of this protein in A. laidlawii cells upon heat shock, which suggests that IbpA not only may participate in the stabilization of individual polypeptides, but may also play a protective role in the maintenance of various cellular structures upon temperature stress.
Insights
This study identifies and characterizes the IbpA protein from Acholeplasma laidlawii as a functional small heat shock protein (sHsp). The IbpA protein protects against protein denaturation and aggregation, suggesting a role in cellular stress response.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Small heat shock proteins (sHsps) are crucial molecular chaperones involved in cellular stress response.
- While sHsps are widespread, their presence in mycoplasmas (Mollicutes) has been limited to the Acholeplasmataceae family.
- The specific role and characterization of sHsps in Acholeplasma laidlawii remained largely unexplored.
Purpose of the Study:
- To clone and functionally characterize a novel small heat shock protein (sHsp) orthologue, the IbpA protein, from Acholeplasma laidlawii.
- To investigate the in vitro chaperone activity of the recombinant IbpA protein.
- To determine the intracellular localization and stress-dependent function of IbpA in A. laidlawii.
Main Methods:
- Cloning and expression of the IbpA protein from Acholeplasma laidlawii.
- In vitro assays to assess the oligomerization and chaperone activity of recombinant IbpA using chemically denatured bovine insulin.
- Immune-electron microscopy to visualize the intracellular localization of IbpA in A. laidlawii cells under heat shock conditions.
Main Results:
- The recombinant IbpA protein demonstrated spontaneous oligomerization in vitro.
- IbpA effectively rescued chemically denatured bovine insulin from aggregation, confirming its chaperone activity.
- Immune-electron microscopy revealed altered intracellular localization of IbpA in A. laidlawii upon heat shock.
Conclusions:
- The IbpA protein from Acholeplasma laidlawii is a functional member of the small heat shock protein family.
- IbpA possesses chaperone activity, protecting proteins from denaturation and aggregation.
- The stress-induced changes in IbpA localization suggest a role in maintaining cellular structures during temperature stress.
