Editorial [Hot Topic: Recent Advances in Protein and Peptide Chemistry Related to Cellular Regulation (Guest Editor: John W. Ho)]

Research in cellular regulation is an important area of study in drug development. This special issue highlights some of the recent advances in protein and peptide chemistry that is related to cellular regulation. The functional role of a protein molecule requires an understanding of its biologic activity involved in cells. The focus is on interpretation of structural information gathered through molecular biology and various techniques. Recent research has provided an abundance of new information on biochemistry of proteins and peptides. It is essential to update our current understanding of some protein structure and function to fully appreciate and apply these findings. This special issue describes some recent work on folding/unfolding of insulin and its structure and function relationship, and a recent progress on research into the integrin βA domain using maltose-binding protein as a fusion tag to prepare quantitative amount of soluble leukocyte integrin βA. This issue also includes a recent study on opioid receptor-like receptor, which utilizes both GOA and GOB for signal transduction. The receptor can utilize GaO variants to inhibit adenylyl cyclase and stimulate protein kinases in HEK293 cells. The study confirmed that the ORL1 receptor could interact with the two variants of GaO to inhibit AC and stimulate ERK1/2. The coupling to G0A/B sheds light on the molecular basis for some of the signaling properties of the ORL1 receptor, including the Ca2+ channels. In addition, site-directed mutagensis study of ferrochelatase of chironomidae showed a considerable difference from mammalian ferrochelatases in enzyme activity and metal binding with copper ions. The study identifies for the first time that the highly conserved H60 in ferrochelatase is a key molecular determinant in directing a catalytically mode of metal interaction in the active site. The functional roles of bovine pancreatic deoxyribonuclease I in the catalytic reaction and the contributions of N- and C-terminal domains in the enzyme folding are also presented. Vogel, etc. reports a study on the complex structures for many types of CaM-binding peptides and some target proteins and the versatility of CaM-target recognition. Leung's paper describes the application of mass spectrometry to the characterization of the signaling proteins in cells. Other studies include various chemical techniques such as x-ray crystallography, synthesis, sequence and proteome analysis to study the functional roles and stability of important proteins. This special issue would provide insights into the methodology and discovery of novel proteins and peptides and their functional roles in cells. It is difficult to detect distant protein family relationships and the presence of different domains by direct comparison of sequences. However, the functional roles of proteins in cells can be determined if the chemical structures of the proteins are known. These protein factors share similar signaling machinery that may change the duration and localization of signals in cells. The study has become critical as efforts proceed to decipher and manage them for beneficial effect. In conclusion, mapping the protein connections and providing useful information about signaling pathways is a challenging work. Using updated knowledge to decipher how proteins play functional roles in cells and change in connectivity to produce fine regulation will require the best tools we can have. Finally, we want to express our appreciation to authors of this special issue. Specially, we wish to thank PPL for giving us the opportunity and help in creating this special issue. We are also grateful to Ms Mandy Chan of CUHK for editorial assistance.