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2D-PAGE analysis: adrenergically regulated pineal protein AIP 37/6 is a phosphorylated isoform of cytosolic malate
J L Weller1, H Jaffe, P H Roseboom
1Section of Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Abstract:
The adrenergic transmitter norepinephrine (NE) dramatically increases the prominence of only two out of the hundreds of [35S]methionine-labeled pineal proteins resolved by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). One of these regulated proteins is AIP 37/6 (37 kDa, pI approximately 6). The labeling of this protein is increased approximately 100-fold by NE. In the study presented here the identity of AIP 37/6 was investigated. The results of microsequencing, immunochemical analysis of 2D-PAGE blots and size exclusion chromatography indicate that AIP 37/6 is an isoform of cytosolic malate dehydrogenase (cMDH; approximately 36.3 kDa; pI approximately 6.5). Associated studies indicate that this isoform is phosphorylated whereas the bulk of cMDH is not. Cotranslational phosphorylation of cMDH is discussed.