Peptide signal amplification

Since there is no PCR-like signal amplification process for proteins or peptides, there must be efficient sample preconcentration... 

Since there is no PCR-like signal amplification process for proteins or peptides, there must be efficient sample pre-concentration steps in the overall process. The low-abundance molecules could be efficiently separated, but in order to cover several-order-of-magnitude concentration ranges, one needs to concentrate these purified dilute, low-abundance species into higher concentration. 

No Cr-dependent enzymes or Cr-binding proteins have been identified to date. However, one chromiumbinding peptide, chromodulin, with the putative sequence pEEEEGDD (where pE is pyroglutamate) has been characterised (Chen, Watson, Gao, Sinha, Cassady, Vincent, 2011), and found to bind 4 chromic ions per peptide. It is proposed that the chromium-loaded chromodulin may function in the amplification system for insulin signalling (Vincent, 2000b) for transporting Cr " " to tissues in an insulin-responsive manner. 

Fig. 1. General scheme for the mechanism of action of many peptide hormones at plasma membrane receptor systems. Such systems include (minimally) a membrane surface receptor at which peptide binding (recognition) occurs, a regulatory protein through which signal transduction occurs, and an amplification system (here represented as adenylate cyclase) which produces the intracellular second messenger (here cyclic AMP) which modulates cellular function...

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