Light at the end of the tunnel – but still a long way to go

September 1, 2011

Proteins always fulfil an essential function for a living cell. In some cases this functional purpose lies not directly within the cell, but embedded within the cell membrane or even outside the cell. In bacterial cells for those kinds of situations the Sec-translocon protein channel comes into action. Since roughly 60% of all drugs more or less interact with such or similar membrane channels, more insights in structure/function relationships of these molecular facilitators is desirable. What does such a channel look like? After overcoming the difficulties of identifying the structure of membrane proteins, a model as in Fig. 1 resulted.

Fig. 1: At the top schematically the hour-glass shape of the SecYEG translocon is displayed. At the bottom the corresponding ribbon structure can be seen together with the ribbon structure of SecA. SecA serves as a molecular motor to propel (at the expense of ATP) the unfolded polypeptide through the channel by a not quite understood mechanism. (top source: Maillard et al. Protein Movement Across Membranes, bottom source: Kusters et al. Quaternary Structure of SecA in Solution and Bound to SecYEG Probed at the Single Molecule Level)

In total the bacterial translocase pathway is composed out of seven proteins. How SecB, SecA, the integral membrane complex SecYEG, SecD, and SecF exactly work together will hopefully become clearer over the years. For my part I will start diving into the matter quite quick now. Maybe I find a piece of the puzzle. And maybe I will find out where I have to put it in order to make the picture even more beautiful and elegant.

A quite handy overview about the topic can be found here at NCBI.

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