Alpha subunit

In addition to intracellular heme-containing proteins, big-conductance calcium-dependent K+ (BKCa) channels and calcium-spark activated transient Kca channels in plasma membrane are also tar geted by CO [3]. As well known, nitric oxide (NO) also activates BKca channels in vascular smooth muscle cells. While both NO and CO open BKCa channels, CO mainly acts on alpha subunit of BKCa channels and NO mainly acts on beta subunit of BKca channels in vascular smooth muscle cells. Rather than a redundant machinery, CO and NO provide a coordinated regulation of BKca channel function by acting on different subunits of the same protein complex. Furthermore, pretreatment of vascular smooth muscle... 

K Channels belong to a class of membrane proteins that form highly K-selective pores in membranes. All known K Channels are composed of several (usually four) pore forming alpha subunits and auxiliary beta subunits. K Channels play an essential role in cellular excitability, being involved in repolarization of Action Potentials and setting the cell resting potential as well as contributing to potassium homeostasis. 

The majority of GPCRs couple to three families of G protein alpha subunits which differ in their ability to activate three distinct primary signaling cascades. The stimulatory G-protein Gas, positively regulates the activity of adenylyl cyclase causing an increase of intracellular cAMP levels as second messenger. In... 

In the present context, a tetramer is a symmetric arrangement of four subunits, which generates K channel. Nearly all known K channels are tetramers of identical or similar alpha subunits often associated with additional beta subunits arranged again in a tetrameric fashion. Some K channels are dimers, but each part of their alpha subunits represents a two-fold repeat of a monomer. 

Hyperkalemic periodic paralysis AD 17q13 Sodium channel alpha subunit... 

Integrins themselves are found on nearly all cells and mediate several physiological responses, such as cell-cell and cell-matrix interactions. Three families of integrins, each family with a common beta subunit in combination with distinct alpha subunits, have been recognized. The beta 1 family, also called very late lymphocyte-activation antigen or VLA, has receptors mediating extracellular matrix interactions with molecules such as collagen, laminin, and fibronectin. Naturally, platelets contain many of the receptors of the beta 1 family. 

Igarashi, K., Fujita, N., and Ishihama, A. (1991). Identification ofa subunit assembly domain in the alpha subunit ofEscherichia coli RNA polymerase. J. Mol. Biol. 218, 1-6. 

Unwin, N., Projection structure of the nicotinic acetylcholine receptor distinct conformations of the alpha subunits, J. Mol. Biol., 257, 586-596, 1996. 

Normal hemoglobin molecules are complex, three-dimensional structures consisting of four chains of amino acids known as polypeptide chains. Two of these chains are known as alpha subunits with 141 amino acid residues each, and the remaining polypeptide chains are the beta subunits with 146 amino acid residues each. The sequences of amino acids in the alpha and beta subunits are different, but fold up via noncovalent interactions to form similar three-dimensional structures. When a polypeptide chain arranges itself in space, i.e., when it folds, amino acids that were far apart in the chain are brought closer in proximity. The final overall shape of the protein molecule is influenced by (1) the amino acids in the chain, and (2) the interactions that are possible between distant amino acids. 

Annunen, P., Helaakoski, T., Myllyharju, J., Veijola, J., Pihlajaniemi, T. and Kivirikko, K.I. (1997) Cloning of the human prolyl 4-hydroxylase alpha subunit isoform alpha(II) and characterization of the type II enzyme tetramer - the alpha(I) and alpha(II) subunits do not form a mixed alpha(I)alpha(II)beta(2) tetramer. Journal of Biobgical Chemistry 272, 17342-17348. 

John, D.C.A., Grant, M.E. and Bulleid, N.J. (1993) Cell-free synthesis and assembly of prolyl 4-hydroxylase - the role of the beta-subunit (pdi) in preventing misfolding and aggregation of the alpha-subunit. EMBOJoumal 2,1587-1595. 

Veijola, J., Koivunen, P., Annunen, P., Pihlajaniemi, T. and Kivirikko, K. (1994) Cloning, baculovirus expression, and characterization of the alpha-subunit of prolyl 4-hydroxylase from the nematode Caenorhabditis elegans - this alpha-subunit forms an active alpha-beta dimer with the human protein disulfide-isomerase beta-subunit. Journal of Biological Chemistry 269, 26746-26753. 

Johnson, K.R., Komuniecki, R., Sun, Y. and Wheelock, M.J. (1992) Characterization of cDNA clones for the alpha subunit of pyruvate dehydrogenase from Ascaris suum. Molecular and Biochemical Parasitology 51, 37—48. 

Wiley, L.J., Weiss, A.S., Sangster, N.C. and Li, Q. (1996) Cloning and sequence analysis of the candidate nicotinic acetylcholine receptor alpha subunit gene tar-1 from Trichostrongylus colubriformis. Gene 182,97—100. 

Matts, R. L., Levin, D. H., and London, I. M. (1983). Effect of phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 on the function of reversing factor in the initiation of protein synthesis. Proc. Natl. Acad. Sci. USA 80, 2559—2563. 

Katsuhiko, M., Owens, J.T., Belyaeva, T.A., Meares, C.F., Busby, S.J.W., and Ishihama, A. (1997) Positioning of two alpha subunit carboxy-terminal domains of RNA polymerase at promoters by two transcription factors. PNAS 94, 11274-11278. 

Miyake, R., Murakami, K., Owens, J.T., Greiner, D.P., Ozoline, O.N., Ishihama, A., and Meares, C.F. (1998) Dimeric association of Escherichia coli RNA polymerase alpha subunits, studied by cleavage of single-cysteine alpha subunits conjugated to iron-(S)-l-[p-(bromoacetamido)benzyl]ethylenediaminetet raacetate. Biochemistry 37(5), 1344-1349. 

Pascual, J.M., and Karlin, A. (1998) State-dependent accessibility and electrostatic potential in the channel of the acetylcholine receptor. Inferences from rates of reaction of thiosulfonates with substituted cysteines in the M2 segment of the alpha subunit./. Gen Physiol. 111(6), 717-739. 

Yamaguchi, T.,Nagahama, M., Itoh,H., Hatsuzawa, K.,Tani, K. and Tagaya, M. Regulation of the Golgi structure by the alpha subunits of heterotrimeric G proteins. FEBS Lett. 470 25-28, 2000. 

Lissens, W., De Meirleir, L., Seneca, S. et al. Mutations in the X-linked pyruvate dehydrogenase (El) alpha subunit gene (PDHA1) in patients with a pyruvate dehydrogenase complex deficiency. Hum. Mut. 15 209-219, 2000. 

Hiemke, C. et al., Expression of alpha subunit genes of nicotinic acetylcholine receptors in human lymphocytes, Neurosci. Lett., 214,171, 1996. 

Amin, J., Brooks-Kayal, A., and Weiss, D. S. (1997) Two tyrosine residues on the alpha subunit are crucial for benzodiazepine binding and allosteric modulation of gamma-aminobutyric acidA receptors. Mol. Pharmacol. 51, 833-841. 

Duncalfe, L. L Carpenter, M. R Smillie, L. B Martin, I. L and Dunn, S. M. (1996) The major site of photoaffinity labeling of the gamma-aminobutyric acid type A receptor by [3H]flunitrazepam is histidine 102 of the alpha subunit../. Biol. Chem. 271,9209-9214. 

Smith, G. B. and Olsen, R. W. (1994) Identification of a [3H]muscimol photoaffinity substrate in the bovine gamma-aminobutyric acidA receptor alpha subunit../. Biol. Chem. 269, 20380-20387. 

Verdoom, T. A. (1994) Formation of heteromeric gamma-aminobutyric acid type A receptors containing two different alpha subunits. Mol. Pharmacol. 45,475 480. 

Trainer VL, McPhee JC, Boutelet-Bochan H, Baker C, Scheuer T, Babin D, Demoute JP, Guedin D, Catterall WA (1997) High affinity binding of pyrethroids to the alpha subunit of brain sodium channels. Mol Pharmacol 51 651-657... 

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