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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KHC(NO)2 by Materials Project

KCH(NO)2 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. K1+ is bonded in a 10-coordinate geometry to four equivalent N1- and six equivalent O2- atoms. There are two shorter (3.10 Å) and two longer (3.22 Å) K–N bond lengths. There are a spread of K–O bond distances ranging from 2.81–2.98 Å. C4+ is bonded in a trigonal planar geometry to two equivalent N1- and one H1+ atom. Both C–N bond lengths are 1.35 Å. The C–H bond length is 1.10 Å. N1- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+, one C4+, and one O2- atom. The N–O bond length is 1.28 Å. H1+ is bonded in a single-bond geometry to one C4+ atom. O2- is bonded in a 1-coordinate geometry to three equivalent K1+ and one N1- atom.

36 MATERIALS SCIENCE↗
NASA NTRS2002

Ca2+-dependent dephosphorylation of kinesin heavy chain on beta-granules in pancreatic beta-cells. Implications for regulated beta-granule transport and insulin exocytosis

The specific biochemical steps required for glucose-regulated insulin exocytosis from beta-cells are not well defined. Elevation of glucose leads to increases in cytosolic [Ca2+]i and biphasic release of insulin from both a readily releasable and a storage pool of beta-granules. The effect of elevated [Ca2+]i on phosphorylation of isolated beta-granule membrane proteins was evaluated, and the phosphorylation of four proteins was found to be altered by [Ca2+]i. One (a 18/20-kDa doublet) was a Ca2+-dependent increase in phosphorylation, and, surprisingly, three others (138, 42, and 36 kDa) were Ca2+-dependent dephosphorylations. The 138-kDa beta-granule phosphoprotein was found to be kinesin heavy chain (KHC). At low levels of [Ca2+]i KHC was phosphorylated by casein kinase 2, but KHC was rapidly dephosphorylated by protein phosphatase 2B beta (PP2Bbeta) as [Ca2+]i increased. Inhibitors of PP2B specifically reduced the second, microtubule-dependent, phase of insulin secretion, suggesting that dephosphorylation of KHC was required for transport of beta-granules from the storage pool to replenish the readily releasable pool of beta-granules. This is distinct from synaptic vesicle exocytosis, because neurotransmitter release from synaptosomes did not require a Ca2+-dependent KHC dephosphorylation. These results suggest a novel mechanism for regulating KHC function and beta-granule transport in beta-cells that is mediated by casein kinase 2 and PP2B. They also implicate a novel regulatory role for PP2B/calcineurin in the control of insulin secretion downstream of a rise in [Ca2+]i.

NASA Discipline Neuroscience↗