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Preliminary crystallographic data for an extracellular proteolytic enzyme from a strain of Arthrobacter
J. ilfol.
Biol.
(1968) 34, 193
Preliminary Crystallographic Data for an Extracellular Proteolytic Enzyme from a Strain of Arthrobacter Arthrobacter strains are common soil bacteria which have an important function in the turnover of various macromolecules in nature. These organisms probably degrade soil proteins to the peptide stage with extracellular proteases. One such enzyme from strain B22 of Arthrobacter with a molecular weight of 23,000 has been purified and crystallized by von Hofsten, van Kley & Eaker (1965). This enzyme is very stable towards heat, urea and extreme pH values and is thus suitable for a structural study of the factors that contribute to the stability of proteins (von Hofsten & Reinhammar, 1965). The purified enzyme used in the present work was a gift from Dr B. von Hofsten. The crystallization from ammonium sulphate solutions using microcells has been described by Zeppezauer, Zeppezauer & Eklund (1968). Square bipyramidal crystals were obtained at pH 7.2 to 8.0 and needle crystals at pH 7.2 to 7.4. X-ray precession photographs of the square bipyramidal crystals showed the crystal system to be orthorhombic. The axial reflexions hO0, 0l~O and 001 were restricted to even values of the indices, but no other systematic absences were observed. The space-group is therefore P212,2, and the unit cell dimensions were found to be a =75-l A; b =85*7 b; c = 115.6 8; V =7*44 x lo5 A3. The density of the crystals was found to be 1.25 g/ml. by the flotation method. Using the molecular weight of 23,000 for the enzyme molecule and assuming that the protein content of the crystals is 55%, the number of molecules per asymmetric unit is calculated to be four. The needle crystals belong to the monoclinic space-group P2, with unit cell dimensions a = 73.3 8; b = 122.6 A; c = 106.4 8; /3=90-O” and V = 9.59 x lo5 A3. There are probably eight molecules per asymmetric unit in this modification. We thank Dr B. von Hofsten for supplying us with the enzyme and Professor I. Lindqvist for the facilities placed at our disposal. This work is supported by grant no. 2767-l from the Swedish National Science Research Council and by a grant from the Knut and Alice Wallenberg Foundation. These grants are gratefully acknowledged. Agricultural College of Sweden Department of Chemistry I Uppsala 7, Sweden Received
16 February
H. EELTJND M. ZEPPEZAUER C.-I. BRXND~~N
1968
REFERENCES von Hofsten, B., van Kley, H. 8s Eaker, D. (1965). Biochim. biophys. Acta, 110, 585. von Hofsten, B. & Reinhammar, B. (1965). Biocltirn. bio@l/s. Acta, 110, 599. Zeppezauer, M., Zeppezauer, E. & Eklund, H. (1968). Arch. Biochem. Biophye. in the press.
193
Biol.
(1968) 34, 193
Preliminary Crystallographic Data for an Extracellular Proteolytic Enzyme from a Strain of Arthrobacter Arthrobacter strains are common soil bacteria which have an important function in the turnover of various macromolecules in nature. These organisms probably degrade soil proteins to the peptide stage with extracellular proteases. One such enzyme from strain B22 of Arthrobacter with a molecular weight of 23,000 has been purified and crystallized by von Hofsten, van Kley & Eaker (1965). This enzyme is very stable towards heat, urea and extreme pH values and is thus suitable for a structural study of the factors that contribute to the stability of proteins (von Hofsten & Reinhammar, 1965). The purified enzyme used in the present work was a gift from Dr B. von Hofsten. The crystallization from ammonium sulphate solutions using microcells has been described by Zeppezauer, Zeppezauer & Eklund (1968). Square bipyramidal crystals were obtained at pH 7.2 to 8.0 and needle crystals at pH 7.2 to 7.4. X-ray precession photographs of the square bipyramidal crystals showed the crystal system to be orthorhombic. The axial reflexions hO0, 0l~O and 001 were restricted to even values of the indices, but no other systematic absences were observed. The space-group is therefore P212,2, and the unit cell dimensions were found to be a =75-l A; b =85*7 b; c = 115.6 8; V =7*44 x lo5 A3. The density of the crystals was found to be 1.25 g/ml. by the flotation method. Using the molecular weight of 23,000 for the enzyme molecule and assuming that the protein content of the crystals is 55%, the number of molecules per asymmetric unit is calculated to be four. The needle crystals belong to the monoclinic space-group P2, with unit cell dimensions a = 73.3 8; b = 122.6 A; c = 106.4 8; /3=90-O” and V = 9.59 x lo5 A3. There are probably eight molecules per asymmetric unit in this modification. We thank Dr B. von Hofsten for supplying us with the enzyme and Professor I. Lindqvist for the facilities placed at our disposal. This work is supported by grant no. 2767-l from the Swedish National Science Research Council and by a grant from the Knut and Alice Wallenberg Foundation. These grants are gratefully acknowledged. Agricultural College of Sweden Department of Chemistry I Uppsala 7, Sweden Received
16 February
H. EELTJND M. ZEPPEZAUER C.-I. BRXND~~N
1968
REFERENCES von Hofsten, B., van Kley, H. 8s Eaker, D. (1965). Biochim. biophys. Acta, 110, 585. von Hofsten, B. & Reinhammar, B. (1965). Biocltirn. bio@l/s. Acta, 110, 599. Zeppezauer, M., Zeppezauer, E. & Eklund, H. (1968). Arch. Biochem. Biophye. in the press.
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