Cataract-causing mutation R233H affects the stabilities of ßB1- and ßA3/ßB1-crystallins with different pH-dependence.

Disease-causing mutations can be stabilizing or destabilizing. Missense mutations of structural residues are generally destabilizing, while stabilizing mutations are usually linked to alterations in protein functions. Stabilizing mutations are rarely identified in mutations linked to congenital cataract, a disease caused by the opacification of the lens. In this research, we found that R233H mutation had little impact on ßB1-crystallin structure, solubility and thermal stability under neutral solution pH conditions. The mutation increased ßB1 stability against guanidine hydrochloride-induced denaturation, suggesting that Arg233 might be a functional residue. Further analysis indicated that the R233H mutation did not affect the formation of ßA3/ßB1 heteromer, but significantly reduced heteromer stability against heat- and guanidine hydrochloride-induced denaturation. The R233H mutation negatively affected the thermal stabilities and aggregatory propensities of ßB1 and ßA3/ßB1 with different pH-dependence, implying that the protonation of His side chains during acidification played a regulatory role in crystallin stability and aggregation. Molecular dynamic simulations indicated that Arg233 is one of the residues forming an inter-subunit ion-pairing network with intrinsically dynamic nature. Based on these observations, we proposed that the highly dynamic ion-pairing network contributed to the tradeoff among ßB1 solubility, stability, aggregatory propensity and function of protecting ßA3.

Cataract-linked mutation R188H promotes ßB2-crystallin aggregation and fibrillization during acid denaturation.

Cataract is characterized by the formation of light-scattering protein aggregates in the lens. ß/γ-Crystallins are the predominant structural proteins in the cytosol of lens fiber cells, and more than fifty ß/γ-crystallin mutations have been linked to autosomal dominant congenital cataract. However, the structural role of these mutations in the formation of the core structures of amorphous aggregates or amyloid-like fibrils has not been elucidated yet. In this research, we studied the effects of the V187M and R188H mutations on the aggregation and fibrillization of ßB2-crystallin during acid denaturation. The behavior of V187M was the same as the WT protein, suggesting that the residue at position 187 contributed little to the aggregation/fibrillization process. R188H promoted the formation of amorphous aggregates at pH above 3 and accelerated fibrillization at pH 3. The distinct behaviors of the mutants suggested that the residue at position 188 might play a regulatory role in ßB2-crystallin aggregation/fibrillization but not reside in the core of the aggregates/fibrils.

[Clinical analysis of prognostic factors for patients with gastrointestinal stromal tumors].

OBJECTIVE: To investigate the prognostic factors for patients with gastrointestinal stromal tumors (GIST). METHODS: From 2000 to 2003, clinical data of 41 cases with GIST were reviewed retrospectively. The clinicopathologic diagnosis was determined by immunochemistry. The relationships of the prognosis with mitotic counts, tumor size and location,range of tumor resection were analyzed. RESULTS: The patients with GIST had pathological section of high expression in CD117, CD34 and vimentin (92.7%, 82.9%, 78%, respectively). Patients with tumor location in intestine, tumor size > 5 cm,mitotic counts > 5/50HPF, incomplete resection had poorer outcome, compared with those with tumor location in stomach and colon,tumor size < or = 5 cm,mitotic counts < or = 5/50HPF and complete resection (all P< 0.05). CONCLUSION: Complete gross resection can improve prognosis for patients with GIST. Tumors with mitotic counts > or = 5/50HPF, tumor size more than 5 cm and tumor location in intestine are poor prognostic factors.

Study of hydrolytic kinetics of the hexachlorostannate anion by two-dimensional 119 Sn exchange spectroscopy.

Two-dimensional 119 Sn exchange spectroscopy was applied to study the hydrolytic kinetics of the hexachloro-stannate anion, SnCl6 2- . Two 119 Sn exchange spectra for SnCl4 · 5H2 O solutions with various HCl concentrations are presented. Magnetization exchanges, which are related to the hydrolysis processes, occur in the SnCl6 2- hydrolysis series. The exchange rate constants, the hydrolysis rate constants and the hydrolysis equilibrium constants were evaluated.