Defining the Substrate Spectrum of the TIM22 Complex Identifies Pyruvate Carrier Subunits as Unconventional Cargos

Mitochondria carrier proteins, which possess six transmembrane spans (TM), are transported by the TIM22 complex. By using a quantitative proteomic approach, Gomkale and Cruz-Zaragoza et al. reveal subunits of the mitochondrial pyruvate carrier (MPC) that possess two or three TMs as unexpected substrates of the carrier pathway

An in vitro system to silence mitochondrial gene expression

The human mitochondrial genome encodes thirteen core subunits of the oxidative phosphorylation system, and defects in mitochondrial gene expression lead to severe neuromuscular disorders. However, the mech- anisms of mitochondrial gene expression remain poorly understood due to a lack of experimental ap- proaches to analyze these processes. Here, we present an in vitro system to silence translation in purified mitochondria. In vitro import of chemically synthesized precursor-morpholino hybrids allows us to target translation of individual mitochondrial mRNAs. By applying this approach, we conclude that the bicistronic, overlapping ATP8/ATP6 transcript is translated through a single ribosome/mRNA engagement. We show that recruitment of COX1 assembly factors to translating ribosomes depends on nascent chain formation. By defining mRNA-specific interactomes for COX1 and COX2, we reveal an unexpected function of the cytosolic oncofetal IGF2BP1, an RNA-binding protein, in mitochondrial translation. Our data provide insight into mitochondrial translation and innovative strategies to investigate mitochondrial gene expression

Mapping protein interactions in the active TOM-TIM23 supercomplex

Nuclear-encoded mitochondrial proteins destined for the matrix have to be transported across two membranes. The TOM and TIM23 complexes facilitate the transport of precursor proteins with N-terminal targeting signals into the matrix. During transport, precursors are recognized by the TIM23 complex in the inner membrane for handover from the TOM complex. However, we have little knowledge on the organization of the TOM-TIM23 transition zone and on how precursor transfer between the translocases occurs. Here, we have designed a precursor protein that is stalled during matrix transport in a TOM-TIM23-spanning manner and enables purification of the translocation intermediate. Combining chemical cross-linking with mass spectrometric analyses and structural modeling allows us to map the molecular environment of the intermembrane space interface of TOM and TIM23 as well as the import motor interactions with amino acid resolution. Our analyses provide a framework for understanding presequence handover and translocation during matrix protein transport

Effect of Pulsed Concentrated Solar Radiation on Seeds and Plants

11-13Role of sunlight for plant growth through photosynthesis is well known. The systematic use of concentrated sunlight is being made in medicine, biology and chemistry since last three decades. To avoid the burning effect of concentrated sunlight, Pulsed Concentrated Solar Radiation (PCSR) was developed, in which seeds of biological objects are exposed intermittently. The PCSR increased the germination, plant growth, development and productivity in many crops with early maturity by 3 to 6 d. The treatment accelerates the metabolism, which leads to active growth of embryo. This treatment has been reported to increase the content of nucleic acids, sugars, vitamins, quality of produce and even acts as a promising mutagenic factor

LAB Industry in India - An Overview

Linear alkyl benzene (LAB) industry in India has undergone a remarkable growth from installed capacity base of 30,000 tpa in 1987 to the present level of 284,000 tpa. This capacity is entirely based on UOP technology i.e. molex process for n-paraffin separation, pacol process for dehydrogenation and HF/heterogeneous catalyst alkylation. There is an emerging need to substitute hazardous HF catalyst by environment friendly solid acid catalyst for the alkylation step in old LAB units. The LAB produced in the country is of international quality barring some undesirable component~ like dialkyltetraline (DAT) for which stringent limits may be incorporated in BIS specification. LAB consumption in India increased from 35,000 tonnes in 1980-81 to 209,000 tonnes in 1996-97. Future demand in the country is projected to increase at a healthy growth rate of 7-8% as against 2-4% world wide. The preseHt self sufficiency level fof this product will no longer be sustainable during the Tenth Plan Period and a shortfall in availability to the extent of 85,000 tonnes is expected by the year 2006-07. There seems to be good potential for export of LAB to Asia Pacific, Africa and CIS countries where LAB sulphonate is not 'I facing threats from other detergents and capacity additions are lagging behind the growth in consumption

Motor recruitment to the TIM23 channel's lateral gate restricts polypeptide release into the inner membrane.

The presequence translocase of the mitochondrial inner membrane (TIM23 complex) facilitates anterograde precursor transport into the matrix and lateral release of precursors with stop-transfer signal into the membrane (sorting). Sorting requires precursor exit from the translocation channel into the lipid phase through the lateral gate of the TIM23 complex. How the two transport modes are regulated and balanced against each other is unknown. Here we show that the import motor J-protein Pam18, which is essential for matrix import, controls lateral protein release into the lipid bilayer. Constitutively translocase-associated Pam18 obstructs lateral precursor transport. Concomitantly, Mgr2, implicated in precursor quality control, is displaced from the translocase. We conclude that during motor-dependent matrix protein transport, the transmembrane segment of Pam18 closes the lateral gate to promote anterograde polypeptide movement. This finding explains why a motor-free form of the translocase facilitates the lateral movement of precursors with a stop-transfer signal