Structure and function of LCI1: a plasma membrane CO2 channel in the Chlamydomonas CO2 concentrating mechanism

Microalgae and cyanobacteria contribute roughly half of the global photosynthetic carbon assimilation. Faced with limited access to CO₂ in aquatic environments, which can vary daily or hourly, these microorganisms have evolved use of an efficient CO₂ concentrating mechanism (CCM) to accumulate high internal concentrations of inorganic carbon (C_i) to maintain photosynthetic performance. For eukaryotic algae, a combination of molecular, genetic and physiological studies using the model organism Chlamydomonas reinhardtii, have revealed the function and molecular characteristics of many CCM components, including active C_i uptake systems. Fundamental to eukaryotic C_i uptake systems are C_i transporters/channels located in membranes of various cell compartments, which together facilitate the movement of C_i from the environment into the chloroplast, where primary CO₂ assimilation occurs. Two putative plasma membrane C_i transporters, HLA3 and LCI1, are reportedly involved in active C_i uptake. Based on previous studies, HLA3 clearly plays a meaningful role in HCO₃^? transport, but the function of LCI1 has not yet been thoroughly investigated so remains somewhat obscure. Here we report a crystal structure of the full‐length LCI1 membrane protein to reveal LCI1 structural characteristics, as well as in vivo physiological studies in an LCI1 loss‐of‐function mutant to reveal the C_i species preference for LCI1. Together, these new studies demonstrate LCI1 plays an important role in active CO₂ uptake and that LCI1 likely functions as a plasma membrane CO₂ channel, possibly a gated channel.     

A Critical Regulatory Role for Macrophage Migration Inhibitory Factor in Hyperoxia-Induced Injury in the Developing Murine Lung

Background

The role and mechanism of action of MIF in hyperoxia-induced acute lung injury (HALI) in the newborn lung are not known. We hypothesized that MIF is a critical regulatory molecule in HALI in the developing lung.

Methodology

We studied newborn wild type (WT), MIF knockout (MIFKO), and MIF lung transgenic (MIFTG) mice in room air and hyperoxia exposure for 7 postnatal (PN) days. Lung morphometry was performed and mRNA and protein expression of vascular mediators were analyzed.

Results

MIF mRNA and protein expression were significantly increased in WT lungs at PN7 of hyperoxia exposure. The pattern of expression of Angiopoietin 2 protein (in MIFKO>WT>MIFTG) was similar to the mortality pattern (MIFKO>WT>MIFTG) in hyperoxia at PN7. In room air, MIFKO and MIFTG had modest but significant increases in chord length, compared to WT. This was associated with decreased expression of Angiopoietin 1 and Tie 2 proteins in the MIFKO and MIFTG, as compared to the WT control lungs in room air. However, on hyperoxia exposure, while the chord length was increased from their respective room air controls, there were no differences between the 3 genotypes.

Conclusion

These data point to the potential roles of Angiopoietins 1, 2 and their receptor Tie2 in the MIF-regulated response in room air and upon hyperoxia exposure in the neonatal lung.     

Dehydration of Chiral α-Amides to Chiral α-Nitriles Under the Appel Reaction Conditions

International Journal of Peptide Research and Therapeutics - An efficient synthesis of Nα-protected amino nitriles from Nα-protected amino acid amides employing Ph3P, I2 and NMM was...     

Synthesis of oligopeptides through O-acyl isopeptide method

The O-acyl isopeptide method has recently gained attention as an efficient protocol for the synthesis of 'difficult sequence' peptides. Herein, synthesis of three oligopeptides of different length, a pentapeptide Gly-Leu-Leu-Ser-Val, a heptapeptide fragment 285-291 of transmembrane (M7-24-T40) Ala-Val-Leu-Ser-Leu-Pro-Leu and a decapeptide, Gly-Leu-Leu-Ser-Val-Leu-Gly-Ser-Val-Ala were demonstrated in solution phase by employing O-acyl isopeptide method. The peptides were established through an efficient pH triggered intramolecular O→N acyl migration under physiological conditions. The reactions were clean and complete in appreciable length of time.     

Carbonyldiimidazole (CDI) mediated synthesis of Nα-protected amino acid azides: application to the one-pot preparation of ureidopeptides

Synthesis of Nα-protected amino acyl azides starting from corresponding acids via the carbonyldiimidazole (CDI) activation is described. The protocol is extended for a one-pot preparation of ureido peptides that circumvents the isolation of acyl azide and isocyanate intermediates. The reaction was accomplished without using any additives and base. The protocol is simple, clean, high yielding and free from racemization.     

Insulin-like growth factor binding proteins and mammary gland development

Mammary gland development is dependent upon insulin-like growth factors (IGFs) as survival factors. The actions of the IGFs are modulated by a family of IGF-binding proteins (IGFBP1-6). Expression of the IGFBPs is both time-dependent and cell-specific during both the developmental phases and the involution of the mammary gland. Although studied extensively in vitro, understanding the roles of IGFBPs in vivo has been difficult, largely due to the fact that IGFBP knock-out mice have no dramatic phenotypes. This review examines the evidence from in vitro studies and the attempts to examine in vivo actions utilising models with IGFBP deficiency or over-expression. In vitro studies demonstrate that IGFBPs can act by inhibition of the survival effects of IGFs, as well as by enhancing the effects of IGFs. Because the IGFBPs are found associated with the extracellular matrix, a role for IGFBPs as a reservoir of IGFs or, alternatively as a potential barrier to IGFs, thereby restricting their entry into particular tissues or cellular compartments was postulated. We also provide evidence with respect to the IGF-independent actions of the IGFBPs which include receptors, nuclear localization, and interaction with the extracellular matrix and cell surface proteins including integrins. We believe that recent findings place some of the IGFBPs in a larger family of extracellular proteins, the secreted cysteine-rich protein (CCN) family, which have similar structural domains (involved in binding to IGFs, extracellular matrix and integrins) and are heavily implicated in tissue re-modeling and morphogenesis.     

Epimerization free synthesis of O-acyl isodipeptides employing COMU

O-Acyl isodipeptides are prepared by coupling Boc-Ser/Thr-OBzl with Fmoc-Xaa-OH employing COMU, well known third generation peptide coupling agent. The reaction proceeds with high yield and the chemical homogeneity of the synthesized molecules were established via chiral HPLC analyses. The O-acyl isodipeptide units play crucial role in the success of ' click peptide' protocol employed for assembling ' difficult sequence' peptides.     

Synthesis and antioxidant activity of 4-[2-(3,5-dimethoxyphenyl)ethenyl]-1,2-benzenediol, a metabolite of Sphaerophysa salsula

4-[2-(3,5-Dimethoxyphenyl)ethenyl]-1,2-benzenediol (7), a stilbene isolated from Sphaerophysa salsula, was synthesized from 3,4-dihydroxybenzaldehyde (1) in five steps in an overall yield of 33%. The spectral data for synthetic 7 are in good agreement with those of the natural product. Hydroxystilbene 7 showed potent antioxidative activity.