J. Demmer et al., MOLECULAR-CLONING OF ERP29, A NOVEL AND WIDELY EXPRESSED RESIDENT OF THE ENDOPLASMIC-RETICULUM, FEBS letters, 402(2-3), 1997, pp. 145-150
We have isolated a full-length cDNA clone for a novel 29 kDa protein t
hat is highly expressed in rat enamel cells. The clone encodes a 259-r
esidue protein, here named ERp29, with structural features (signal pep
tide and a variant endoplasmic reticulum-retention motif, KEEL) that i
ndicate it is a reticuloplasmin. ERp29 has limited homology with prote
in disulfide isomerase and its cognates, but lacks their characteristi
c thioredoxin-like catalytic moiety and calcium-binding motifs. ERp29
mRNA was expressed in all rat tissues tested, and a homologous transcr
ipt was detected in other animal livers (primate, ruminant, marsupial)
. In human hepatoma cells, ERp29 mRNA expression was not increased by
stresses (tunicamycin, calcium ionophore) that induced other reticulop
lasmins. We conclude that ERp29 is a new, highly conserved member of t
he reticuloplasmin family which is widely expressed. The apparent lack
of both calcium binding properties and stress responsiveness distingu
ish ERp29 from all major reticuloplasmins characterised to date.