Extreme thermostability of tarantula hemocyanin

Abstract

Biotops with extreme temperatures such as deserts force animals to avoid or escape high temperatures by biochemical, behavioural or morphological adaptation. In this context we tested the resistance to heat of the oxygen carrier hemocyanin from the ancient tarantula Eurypelma californicum, which is found in arid zones of North America. Differential scanning calorimetry, light scattering, crossed immunogelelectrophoresis and oxygen binding experiments show that the 24-meric hemocyanin is conformationally stable and fully functioning at temperatures up to 90°C. Our results demonstrate that the cation-mediated state of oligomerization is not only crucial for the high cooperativity of oxygen binding of this hemocyanin, but also for its extreme stability in the physiological temperature and pH range.

Bacillus Thermoamyloliquefaciens KP1071 α‐Glucosidase II is a Thermostable Mr 540000 Homohexameric α‐Glucosidase with both Exo‐α‐1,4‐Glucosidase and Oligo‐1,6‐Glucosidase Activities

“…These remarkable properties of the a-glucosidase I1 are intrinsic, as the cloned enzyme is found to be molecularly and functionally identical with the native one [20]. Its extreme stability is probably the result of the combined effects of its state of oligomerization and an elevated stability of its subunits compared with the monomeric enzymes [28], since the subunit aggregation in proteins is accompanied by an increase in the optimization of hydrophobic interactions [29], and since the a-glucosidase I1 has more hydrophobic residues (62.3 mol/100 mol), while less hydrogen-bond (46.1 mo1/100 mol) and ionic-bridge formers (26.7 mo1/100 mol), than the exo-a-1,4-glucosidase and the oligo-l,6-glucosidase (Table 3) [7, 81. Hydrophobic interactions are considered predominantly responsible for protein thermostability, whereas hydrogen-bonding and charge-charge interactions weakened at elevated temperatures [30].…”

Synchrotron SAXS Studies on the Structural Stability of Carcinus aestuarii Hemocyanin in Solution

“…As no dodecameric Hc has been so far crystallized, this structure has been obtained by the addition of two hexamers superimposed to each other, with the threefold symmetry axis of one hexamer perpendicular to the same axis of the other hexamer (van Holde and Miller, 1995;Taveau et al, 1997). Finally, to form icosatetramers, two dodecamers have been assembled parallel to each other, but staggered 58 in the transversal axis (Sterner et al, 1995). These structures are reported in the gallery of Fig.…”

“…The dissociation equilibrium between monomers, hexamers, and higher order oligomers are shown to affect the oxygen binding of Hcs (Markl and Decker, 1992;Dainese et al, 1998;Molon et al, 2000). In addition, several studies have been addressed to the problem of the conformational stability of these proteins versus various physicochemical conditions, such as pressure (Bonafe et al, 1994) or temperature (Sterner et al, 1995;Beltramini et al, 1999), or the presence of solutes, such as the salts of the Hofmeister's series or ureas (Herskovits et al, 1984). Denatured states of proteins have become increasingly more attractive and interesting because they play an important role in protein folding, transport across membranes, and proteolysis (Dill and Shortle, 1991).…”

Extraordinary stability of hemocyanins from L. polyphemus and E. californicum studied using infrared spectroscopy from 294 to 20 K

“…Both proteins were previously shown to be very stable with respect to heat-induced unfolding, with transition temperatures at 92 and 93 1C respectively. 9,10 In control experiments, we obtained (91 and 93 1C, respectively, see Fig. S6, ESI †).…”

“…A remarkable stability of the oxy-forms of Limulus polyphemus and Eurypelma californicum Hcs (91 and 92.5 1C respectively) was revealed using differential scanning spectroscopy. 9,10 Eurypelma californicum is a spider found in the deserts of southwest North America, a particularly hostile environment which is characterized by large temperature fluctuations between day and night. E. californicum Hc is a 24-mer complex with a molecular mass of 1.7 MDa including seven types of subunits.…”