title: Fibrinogen residue γAla341 is necessary for calcium binding and 'A-a' interactions.
abstract: The fibrinogen γ-module has several important sites relating to fibrinogen function, which include the high affinity calcium binding site, hole 'a' that binds with knob 'A', and the D:D interface. Residue γAla341, which is located in the vicinity of these sites, is altered in three variant fibrinogens: fibrinogen Seoul (γAla341Asp), Tolaga Bay (γAla341Val), and Lyon III (γAla341Thr). In order to investigate the impaired polymerisation of fibrinogens γAla341Asp and γAla341Val to understand the role of γAla341 in fibrin polymerisation and fibrinogen synthesis, we have expressed γAla341Asp and γAla341Val in Chinese hamster ovary (CHO) cells, purified these fibrinogens from the culture media and performed biochemical tests to elucidate their function. Expression in CHO cells was similar for these variants. For both variants the kinetics of thrombin-catalysed FpA release was not different from normal fibrinogen, while FpB release was slower than that of normal. Thrombin-catalysed polymerisation of both variants was dependent on the calcium concentration. At physiologic calcium (1 mM) the variants showed impaired polymerisation with a longer lag period and a slower Vmax than normal fibrinogen. Scanning electron micrographs showed the clots were less organised than normal, having thicker and more twisted fibers, and larger pores. Analysis by SDS-PAGE showed that factor XIIIa-catalysed γ and α chain cross-linking was delayed, and plasmin-catalysed lysis was not reduced by the presence of 5 mM calcium or 5 mM GPRP (Gly-Pro-Arg-Pro). Our data indicate that fibrinogen residue γAla341 is important for the proper conformation of the γ-module, maintaining calcium-binding site and 'A-a' interactions.
authors.affiliation: Department of Laboratory Medicine, Soon Chun Hyang University Hospital, Seoul, Republic of Korea. rpark@schmc.ac.kr
authors.forename: Rojin
authors.initials: R
authors.lastname: Park
authors.forename: Lifang
authors.initials: L
authors.lastname: Ping
authors.forename: Jaewoo
authors.initials: J
authors.lastname: Song
authors.forename: Sung-Yu
authors.initials: SY
authors.lastname: Hong
authors.forename: Tae-Youn
authors.initials: TY
authors.lastname: Choi
authors.forename: Jong-Rak
authors.initials: JR
authors.lastname: Choi
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Gorkun
authors.forename: Susan T
authors.initials: ST
authors.lastname: Lord
mesh_terms: D000409:Alanine; D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid; D001665:Binding Sites; D001777:Blood Coagulation; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004591:Electrophoresis, Polyacrylamide Gel; D026122:Factor XIIIa / Q000378:metabolism; D005340:Fibrinogen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015241:Fibrinogens, Abnormal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D005344:Fibrinopeptide A / Q000378:metabolism; D005345:Fibrinopeptide B / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009842:Oligopeptides / Q000378:metabolism; D011487:Protein Conformation; D055503:Protein Multimerization; D021122:Protein Subunits; D013917:Thrombin / Q000378:metabolism; D014162:Transfection; D014633:Valine
chemical_list: D015241:Fibrinogens, Abnormal; D009842:Oligopeptides; D021122:Protein Subunits; C525592:fibrinogen Tolaga Bay; D005344:Fibrinopeptide A; D001224:Aspartic Acid; D005345:Fibrinopeptide B; C034585:glycyl-prolyl-arginyl-proline; D005340:Fibrinogen; D026122:Factor XIIIa; D013917:Thrombin; D005341:Fibrinolysin; D014633:Valine; D000409:Alanine; D002118:Calcium