18 research outputs found
Inventory and distribution of Oligochaeta (Annelida, Clitellata) in first-order streams in preserved areas of the state of Minas Gerais, Brazil
The invertebrate's community in adjacent Alto Iguaçu's anthropic lakes of different environmental factors
Occurence of oligochaeta living on larvae of odonata from ipeúna (São Paulo state, Brazil)
Naididae (Annelida, Oligochaeta) associated with briophytes in Brotas, State of São Paulo, Brazil
Characterization of the β-chain N-terminus heterogeneity and the α-chain C-terminus of human platelet GPIIb. Posttranslational cleavage sites
4 pags, 4 figsHuman platelet glycoprotein IIb (GPIIb) and IIIa (GPIIIa) form a Ca2+-dependent heterodimer, the integrin GPIIb/IIIa, which functions as the fibrinogen receptor at the surface of activated platelets. GPIIB and GPIIIa are synthesized as single polypeptides from single messages and their amino acid sequences were derived from their cDNAs. The GPIIb precursor is proteolytically processed to yield the known disulphide-bonded two-chain (GPIIbα and GPIIbβ) covalent structure found in mature GPIIb. Our present protein chemical and mass spectrometric analyses indicate that the GPIIb precursor is proteolytically cleaved at two or three sites, to give rise to an homogeneous α-chain (GPIIb 1-856) single disulphidebonded to one of the two β-chains, which are present in a nearly 1:1 ratio: GPIIb β1 (860-1008), with pyroglutamic acid as its blocked N-terminal residue; and GPIIbβ2 (872-1008), with the already known N-terminal sequence. These results satisfy the previously observed electrophoretic size-heterogeneity of the β-chain, confirmed the potential cleavage sites in the junction region, and indicate a probable dual proteolytic processing of GPIIb, which may be relevant to the rest of the two-chain α-subunits of the integrin family. © 1990.This work was supported by the DGICYT (PB 860629 and PM 88-0022) and an Acción Integrada Hispano-Alemana (1989-1990 43A).Peer reviewe