Expression of multiple alpha1-antitrypsin-like genes in hibernating species of the squirrel family.
In the chipmunk, a mammalian hibernator, a 140 kDa protein complex found in the blood, drastically decreases in concentration during hibernation. This complex contains four species of proteins, HP-20, -25, -27 and -55. In the present study, cDNA clones coding for the chipmunk HP-55 were isolated from a liver cDNA library. Sequence analysis revealed that HP-55 is produced as a precursor protein of 413 amino acids (aa), that it has a signal peptide of 24 aa, and that it contains four potential N-glycosylation sites. The deduced aa sequence shows 63% identity with that of rat alpha1-antitrypsin (alpha1-AT); however, the sequence corresponding to the reactive center P1-P1' residues was found to be Met-Leu, whereas it is Met-Ser in the rat alpha1-AT. During screening of the chipmunk liver cDNA library, four other related classes of cDNA clones were obtained, each also coding for an alpha1-AT-like protein. In spite of more than 86% overall aa sequence identity among the five chipmunk alpha1-AT-like proteins, they are highly divergent in the putative reactive center region; the putative P1-P1' sequences are Met-Leu (HP-55 or CM55-ML), Met-Met (CM55-MM), Met-Ser (CM55-MS), Ser-Ile (CM55-SI) and Ser-Thr (CM55-ST). Each of the alpha1-AT-like protein mRNAs was expressed in chipmunk liver, and the HP-55 mRNA level was greatly reduced during hibernation. Genomic Southern blot analysis and screening of a liver cDNA library from another hibernating squirrel species, the ground squirrel, also revealed expression of multiple members of the alpha1-AT gene family, whereas analysis of a cDNA library from a non-hibernating species, the tree squirrel, found only a single alpha1-AT gene.
Takamatsu
N
N
Department of Biosciences, School of Science, Kitasato University, Kanagawa, Japan. takamatu@jet.sci.kitasato-u.ac.jp
Kojima
M
M
Taniyama
M
M
Ohba
K
K
Uematsu
T
T
Segawa
C
C
Tsutou
S
S
Watanabe
M
M
Kondo
J
J
Kondo
N
N
Shiba
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary; D015870:Gene Expression; D006605:Hibernation; D006801:Humans; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D051381:Rats; D012589:Sciuridae / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D000515:alpha 1-Antitrypsin / Q000235:genetics*
D018076:DNA, Complementary; D000515:alpha 1-Antitrypsin