1BZ5

EVIDENCE OF A COMMON DECAMER IN THREE CRYSTAL STRUCTURES OF BPTI, CRYSTALLIZE FROM THIOCYANATE, CHLORIDE OR SULFATE

Summary for 1BZ5

• Entry DOI: 10.2210/pdb1bz5/pdb
• Descriptor: PANCREATIC TRYPSIN INHIBITOR, SULFATE ION (3 entities in total)
• Functional Keywords: bovine pancreatic trypsin inhibitor, pentameric molecule, hydrolase inhibitor
• Biological source: Bos taurus (cattle)
• Cellular location: Secreted: P00974
• Total number of polymer chains: 5
• Total formula weight: 32926.03

Authors

Hamiaux, C.,Prange, T.,Ries-Kautt, M.,Ducruix, A.,Lafont, S.,Astier, J.P.,Veesler, S. (deposition date: 1998-11-05, release date: 1998-11-11, Last modification date: 2024-10-30)

Primary citation

Hamiaux, C.,Perez, J.,Prange, T.,Veesler, S.,Ries-Kautt, M.,Vachette, P.
The BPTI decamer observed in acidic pH crystal forms pre-exists as a stable species in solution.
J.Mol.Biol., 297:697-712, 2000

PubMed Abstract: Bovine pancreatic trypsin inhibitor (BPTI) crystallizes under acidic pH conditions in the presence of thiocyanate, chloride and sulfate ions, yielding three different polymorphs in P2(1), P6(4)22 and P6(3)22 space groups, respectively. In all three crystal forms, the same decamer is found in the packing (ten BPTI molecules organized through two perpendicular 2-fold and 5-fold axes as a well-defined and compact object) in contrast to the monomeric crystal forms observed at basic pH conditions. The crystallization of BPTI under acidic conditions (pH 4.5) was investigated by small angle X-ray scattering with both under- and supersaturated BPTI solutions. Data showed the oligomerization of BPTI molecules under all investigated conditions. Accordingly, various mixtures of discrete oligomers (n=1 to 10) were considered. Calculated scattering curves were obtained using models based on the crystallographic structures, and the experimental patterns were analyzed as a linear combination of the model curves using a non-linear curve fitting procedure. The results, confirmed by gel filtration experiments, unambiguously demonstrate the co-existence of two different BPTI particles in solution: a monomer and a decamer, with no evidence of any other intermediates. Moreover, using both approaches, the fraction of decamers was found to increase with increasing salt concentration, even beyond the solubility curve. We therefore propose that at acidic pH, BPTI crystallizes following a two step process: decamers are first built in under- and supersaturated solutions, upon which crystal growth proceeds by decamer stacking. Indeed, those BPTI crystals should best be described as "BPTI decamer" crystals.

PubMed: 10731422
DOI: 10.1006/jmbi.2000.3584

Experimental method

X-RAY DIFFRACTION (2.58 Å)