Thermal Stability of Cytochromec₅of Pressure-SensitiveShewanella livingstonensis

Abstract

Cytochrome c₅ of pressure-sensitive Shewanella livingstonensis (SL cytc₅) exhibits lower thermal stability than a highly homologous counterpart of pressure-tolerant Shewanella violacea. This stability difference is due to an enthalpic effect that can be attributed to the amino acid residue at position 50 (Leu or Lys). These cytc₅ proteins are appropriate materials for understanding the protein stability mechanism.

The Respiratory System of the PiezophilePhotobacterium profundumSS9 Grown under Various Pressures

“…Many y To whom correspondence should be addressed. Fax: +81-3-5317-9433; E-mail: htamegai@chs.nihon-u.ac.jp studies have been carried out on the respiratory system of S. violacea and on related strains for comparison, [19][20][21][22] but it remains unknown whether this phenomenon observed in S. violacea is universal to piezophiles.…”

Comparative study on stabilization mechanism of monomeric cytochrome c5 from deep-sea piezophilic Shewanella violacea

“…15) Variant proteins were prepared from the E. coli cells by the methods described previously. 7,9) Thermal stability measurements. Thermal denaturation experiments were performed by DSC.…”

“…In order to elucidate the mechanism underlying the stability difference between the homologous SVcytc 5 and SLcytc 5 proteins observed previously, 9) the overall crystal structure of the SVcytc 5 protein was successfully determined by the molecular replacement method using the A. vinelandii cytochrome c 5 structure 16) as a search model, and was refined to 1.78 Å resolution. As a result, an asymmetric unit of the crystal was found to contain two molecules of SVcytc 5 ; one being coordinated with imidazole to the heme and the other with the original Met-53 ( Fig.…”

“…As to monomeric proteins from Shewanella species, dihydrofolate reductases 6) and cytochromes c 5 [7][8][9][10] have been used for comparative protein studies so far. In particular, Shewanella cytochrome c 5 is one of the well-known globular class I cytochromes c that have been extensively studied in terms of protein stability by means of various methods such as differential scanning calorimetry (DSC), circular dichroic (CD) spectroscopy, dielectric relaxation spectroscopy, 11,12) and molecular dynamics simulation.…”

“…13) Using the DSC and CD methods, we have measured the thermal stabilities of cytochromes c of various bacterial sources from a variety of environments. 14,15) Specifically, cytochrome c 5 from piezophilic deep-sea Shewanella violacea (SVcytc 5 ) exhibited high stability compared with the homologous cytochrome c 5 from piezo-sensitive shallow-water Shewanella livingstonensis (SLcytc 5 ), 9) indicating that the pressure adaptation of these Shewanella species reflects the difference in stability between SVcytc 5 and SLcytc 5 .…”