Corrigendum to “Small heat shock protein Hsp27 protects myosin S1 from heat-induced aggregation, but not from thermal denaturation and ATPase inactivation” [FEBS Lett. 582 (2008) 1407–1412]

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There are two contradictory viewpoints on the effect of two different small heat shock proteins (sHsp) on thermal inactivation of myosin. According to Melkani et al. [1] commercial αB-crystallin (isolated from bovine lens) prevents both thermal aggregation and inactivation of chicken skeletal myosin, whereas our data indicate that recombinant human Hsp27 (expressed in Escherichia coli) effectively prevents aggregation, but does not affect thermal denaturation of rabbit skeletal myosin S1 and inactivation of its ATPase. In order to solve this discrepancy we analyzed the effect of recombinant human αB-crystallin (expressed in E. coli) on aggregation and inactivation of myosin S1. As in the case with Hsp27, we found that αB-crystallin prevented aggregation, but was unable to protect myosin S1 from heat-induced denaturation. Meanwhile, Dr. Bernstein’s group tested the effect of commercially available recombinant Hsp27 (expressed in E. coli) on thermal denaturation and aggregation of chicken muscle myosin (Dr. Bernstein, personal communication). In good agreement with our data, they found that Hsp27 prevents aggregation, but fails to prevent thermal denaturation of myosin. At the same time, the data of Dr. Bernstein’s group indicate that lens αB-crystallin that was retested simultaneously showed the ability to protect myosin against both thermal denaturation and aggregation. Although the contradiction regarding αB-crystallin remains unresolved, we suppose that utilization of different sources of sHsp (bacterially expressed recombinant vs. isolated from native lens tissue), a priori different methods of sHsp purification, different substrates (rabbit skeletal S1 vs. intact chicken myosin), different methods of ATPase measurements (colorimetric phosphate determination vs. extraction and measurement of radioactive phosphate) etc. makes impossible direct and unequivocal comparison of results obtained in two laboratories. Therefore criticism of Melkani et al. [1] that was presented in our paper was not completely warranted.

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1. Melkani GC, Cammarato A, Bernstein SI. αB-Crystallin maintains skeletal muscle myosin enzymatic activity and prevents its aggregation under heat-shock stress. J. Mol. Biol. 2006;358:635–645
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