Thermal stability properties of an antifreeze protein from the desert beetle Microdera punctipennis.

An insect antifreeze protein gene Mpafp698 was cloned by the RT-PCR approach from the desert beetle Microdera punctipennis. The gene was constructed and heterogeneously expressed in Escherichia coli as fusion proteins, His-MpAFP698, glutathione S-transferase (GST)-MpAFP698, and maltose-binding protein (MBP)-MpAFP698. The thermostability and thermal hysteresis activity of these proteins were determined, with the aim of elucidating the biological characteristics of this protein. The approximate thermal hysteresis (TH) value of the purified His-MpAFP698 was 0.37 degrees C at 0.84 mg/ml, and maintained approximately 95.7% of the TH activity at 100 degrees C for 5 min. Furthermore, heat incubation showed that MBP-MpAFP698 was 10 degrees C more thermostable than MBP protein, indicating that MpAFP698 could, to some extent, improve the thermal stability of the fused partner MBP protein. This study suggests that MpAFP698 has a high thermal stability and could be used to improve the thermal stability of the less stable proteins by producing fusion proteins, which could be used for biotechnological purposes. Copyright 2009 Elsevier Inc. All rights reserved.