Testis-specific expression of mRNAs for a unique human type 1 hexokinase lacking the porin-binding domain.
Several enzymes in the glycolytic pathway are reported to have spermatogenic cell-specific isozymes. We reported recently the cloning of cDNAs representing three unique type 1 hexokinase mRNAs (mHk1-sa, mHk1-sb, and mHk1-sc) present only in mouse spermatogenic cells and the patterns of expression of these mRNAs (Mori et al., 1993: Biol Reprod 49:191-203). The mRNAs contain a spermatogenic cell-specific sequence, but lack the sequence for the porin-binding domain that somatic cell hexokinases use to bind to a pore-forming protein in the outer mitochondrial membrane. We now report the cloning of cDNAs representing three unique human type 1 hexokinase mRNAs (hHK1-ta, hHK1-tb, and hHK1-tc) expressed in testis, but not detected by Northern analysis in other human tissues. These mRNAs also contain a testis-specific sequence not present in somatic cell type 1 hexokinase, but lack the sequence for the porin-binding domain. The hHK1-tb and hHK1-tc mRNAs each contain an additional unique sequence. The testis-specific sequence of the human mRNAs is similar to the spermatogenic cell-specific sequence of the mouse mRNAs. Furthermore, Northern analysis of RNA from mouse, hamster, guinea pig, rabbit, ram, human, and rat demonstrated expression of type 1 hexokinase mRNAs lacking the porin-binding domain in the testes of these mammals. These results suggest that hexokinase may have unique structural or functional features in spermatogenic cells and support a model proposed by others for hexokinase gene evolution in mammals.
Mori
C
C
Department of Anatomy, Faculty of Medicine, Kyoto University, Japan.
Nakamura
N
N
Welch
J E
JE
Shiota
K
K
Eddy
E M
EM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D006224:Cricetinae; D004247:DNA; D015870:Gene Expression; D006168:Guinea Pigs; D006593:Hexokinase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D018272:Porins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013737:Testis / Q000201:enzymology*
D018272:Porins; D012333:RNA, Messenger; D004247:DNA; D006593:Hexokinase