Molecular medicine - To be or not to be

An Outlook on the Complexity of Protein Morphogenesis in Health and Disease

The study of the mechanisms whereby proteins achieve their native functionally competent conformation has been a key issue in molecular biosciences over the last 6 decades. Nevertheless, there are several debated issues and open problems concerning some aspects of this fundamental problem. By considering the emerging complexity of the so-called “native state,” we attempt hereby to propose a personal account on some of the key topics in the field, ranging from the relationships between misfolding and diseases to the significance of protein disorder. Finally, we briefly describe the recent and exciting advances in predicting protein structures from their amino acid sequence.

Engineering a Facile Aptamer "Molecule-Doctor" with Hairpin-Contained I-Motif Enables Accurate Imaging and Killing of Cancer Cells

Herein, we subtly engineered a pH and membrane receptor dual-activatable aptamer therapeutic for bispecific tumor cell imaging and in situ drug release by utilizing a hairpin-contained i-motif as the acid-responsive element to be complementary with a tumor-targeted aptamer, named as an aptamer "molecule-doctor" (pH-Apt-MD). Specifically, the pH-Apt-MD consisted of two DNA strands, where the Apt-sgc8c was labeled with AF488 and Cy3 at its 5'- and 3'-end, respectively. The I-strand, a hairpin-contained i-motif, was complementary to the Apt-sgc8c strand partially, labeled with a BHQ2 in the middle, thus generating Cy3 with quenched fluorescence and only AF488-emitted fluorescence. The double-helix region of pH-Apt-MD was designed rich in GC bases, providing sites for doxorubicin (Dox) intercalation. Once target cells were encountered, the pH-Apt-MD disassembled due to the specific recognition of the aptamer and conformation change of the i-motif, with activated fluorescence resonance energy transfer (FRET) signals between AF488 and Cy3, accompanied by Dox release in situ. Benefiting from the design of the hairpin-contained i-motif, the pH-Apt-MD presented a narrow pH response range (pH 6.0-6.8) with a transition midpoint (pH^T) of 6.50 ± 0.04. Furthermore, living cell studies revealed that the stimuli-responsive FRET signal activation of pH-Apt-MD was successfully achieved on the HCT116 cell surface with ultralow background and enhanced imaging contrast. Then, the cytotoxicity experiments proved that accurate drug release and cell killing were realized to target cells in an acidic microenvironment. As a facile double stimuli-responsive strategy, the pH-Apt-MD may hold great promise for application in precise diagnosis and therapy of cancer cells.

The unique structural features of carbonmonoxy hemoglobin from the sub-Antarctic fish Eleginops maclovinus

Tetrameric hemoglobins (Hbs) are prototypical systems for the investigations of fundamental properties of proteins. Although the structure of these proteins has been known for nearly sixty years, there are many aspects related to their function/structure that are still obscure. Here, we report the crystal structure of a carbonmonoxy form of the Hb isolated from the sub-Antarctic notothenioid fish Eleginops maclovinus characterised by either rare or unique features. In particular, the distal site of the α chain results to be very unusual since the distal His is displaced from its canonical position. This displacement is coupled with a shortening of the highly conserved E helix and the formation of novel interactions at tertiary structure level. Interestingly, the quaternary structure is closer to the T-deoxy state of Hbs than to the R-state despite the full coordination of all chains. Notably, these peculiar structural features provide a rationale for some spectroscopic properties exhibited by the protein in solution. Finally, this unexpected structural plasticity of the heme distal side has been associated with specific sequence signatures of various Hbs.