NMR Studies of the Dynamics of Nitrophorin 2 Bound to Nitric Oxide.
Related Articles NMR Studies of the Dynamics of Nitrophorin 2 Bound to Nitric Oxide.
Biochemistry. 2013 Oct 11;
Authors: Muthu D, Berry RE, Zhang H, Walker FA
Abstract
The Rhodnius nitrophorins are ?-barrel proteins of the lipocalin fold with a heme protruding from the open end of the barrel. They are found in the saliva of the blood-sucking insect Rhodnius prolixus, which synthesizes and stores nitric oxide in the salivary glands, where NO is bound to iron. NO is released by dilution and pH rise when the insect spits its saliva into the tissues of a victim, to aid in obtaining a blood meal. In the adult insect there are four nitrophorins, NP1-NP4. At pH 7.3, NP4 releases NO 17 times faster than does NP2. A number of crystal structures of the least abundant protein, NP4, are available. These structures have been used to propose that two loops between adjacent ?-strands at the front opening of the protein, the A-B and G-H loops, determine the rate of NO release. In order to learn how the protein loops contribute to release of NO for each of the nitrophorins, the dynamics of these proteins are being studied in our laboratory. In this work, NP2-NO has been investigated by pico- to nanosecond and micro- to millisecond NMR techniques at three pH values, 5.0, 6.5, and 7.3. It is found that at pH 5.0 and 6.5 NP2-NO is very rigid and only a few scattered residues show isolated dynamics, while at pH 7.3 somewhat more dynamics are observed. Comparison to other lipocalins shows that all are relatively rigid, and that the dynamics of lipocalins are much more subtle than those 2wof mainly ?-helical proteins.
PMID: 24116947 [PubMed - as supplied by publisher]
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