Immobilization and AFM of single 4×6-mer tarantula hemocyanin molecules

Structural and Conformational Analysis of Scorpion (Buthus sindicus) Hemocyanin Using Low Resolution Techniques

“…cally related scorpion A. australis hemocyanin calculated from electron microscopy as 92.2 Å has recently been corrected to 88.5 Å [27,29]. Unfortunately, we could not manage yet the comparison in terms of shape calculation of the oxygenated/deoxygenated states of scorpion native hemocyanin from the SAXS data alone (also not reported for any other hemocyanin due to the enormous size of the molecule) but our EM studies and identical Rg values confirm the previous hypothesis that hemocyanin become less compact upon oxygenation and there is a sharp conformational switch in terms of flexible tilting in the two identical 2x (2x6-mers) half-molecules against each other in the native 4x6-mers [24][25][26][28][29]. The reasons for this discrepancy be- 86.5 Å ± 0.5) confirm the previous data suggesting that the oxygenated hemocyanin is longer than the deoxygenated hemocyanin by almost 2 Å [28][29].…”

“…A possibly 45° view of the native molecule is also presented in Fig. Recently, Erker et al [24] demonstrated a very similar tilting effect using atomic force microscopy (AFM) in tarantula (E. californicum) 4x6mers native oxygenated hemocyanin while the deoxygenated native molecule revealed a more cubic, top view which is roughly square and flat structure. On the other hand, Fig.…”

“…4A) has been calculated from the scattering profile alone assuming a two-fold symmetry which is not exactly true but acceptable for the resolution (L=6) used for the shape restoration [22][23]. 2) as well as previous independent studies by various authors [24][25][26]28]. Moreover, molecular envelope calculated for the native oxygenated hemocyanin also depicts an apparent slight tilt of the 2x6mers with respect to the rest of half molecule within the native 2x (2x6-mers) assembly and nicely complement our EM results (Fig.…”

“…In order to fully understand these cooperative interactions at molecular level, structures and the molecular transitions of these conformations must be recognized [8,17,36,[41][42]. Likewise, AFM provides relatively moderate resolution (> 10 Å) under conditions which are more physiological than vacuum but less than in solution due to its inherent requirement for solid and flat surface for immobilization [24,44]. These low resolution techniques (EM, AFM and SAS) though provide information about the protein structure differ a great deal in terms of resolution and experimental conditions.…”

The molecular heterogeneity of hemocyanin: Structural and functional properties of the 4×6-meric protein of Upogebia pusilla (Crustacea)

“…Two models are known for the ikosatetrameric Hc: the first one refers to chelicerate 4 × 6-mers, fully described for the scorpion Androctonus australis (Lamy et al, 1981) and the tarantula E. californicum (Erker et al, 2006;Voit et al, 2000); the second model has been proposed to describe the thalassinidean shrimps Hc, notably in Callianassa californiensis (Cavellec et al, 1990). It was shown by multivariate statistical analysis applied to computer aligned electron microscopic images that the 4 × 6 Hcs of A. australis and E. californicum are very similar (Bijholt et al, 1982) and fit the model earlier derived for the 4 × 6 half molecules of Limulus polyphemus.…”