Biochemical mechanisms of NO signalling

How does cGMP bring about relaxation of vascular smooth muscle Several mechanisms, all of which involve PKG, have been proposed none of them is at present certain to be the major one. Moreover, while several relevant changes in protein phosphorylation have been observed, it is not clear at present whether they are caused by PKG directly or by intervening secondary kinases. 

In smooth muscle, contraction is controlled by the phosphorylation state of the myosin regulatory light chain. The extent of this phosphorylation will depend on the regulatory states of both myosin light chain kinase (MLCK) and of 

Does S-nitrosylation really have a regulatory role in the cell This raises the question how specific protein S-nitrosylation might be. From the non-enz5miatic nature of the chemistry discussed above, one might expect S-nitro-sylation to be a very indiscriminate process, which would amount to a lot of noise in the signal - and thus, probably. 

It has been claimed that S-nitrosylation may have a similarly fundamental regulatory role as protein phosphorylation has. Is this claim substantiated by the findings presented My personal impression is that it is not. However, this area is presently under intense investigation, and protein nitro- 

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