Molecular cloning and tissue distribution of keratocan. Bovine corneal keratan sulfate proteoglycan 37A.
Previous studies showed that the keratan sulfate-containing proteoglycans of bovine corneal stroma contain three unique core proteins designated 37A, 37B, and 25 (Funderburgh, J. L., Funderburgh, M. L., Mann, M. M., and Conrad, G. W. (1991) J. Biol. Chem. 266, 14226-14231). Degenerate oligonucleotides designed from amino acid sequences of the 37A protein were used to screen a cDNA expression library from cultured bovine keratocytes. A cDNA clone coding for keratocan, a 37A protein, was isolated and sequenced. The deduced keratocan amino acid sequence is unique but related to two other keratan sulfate-containing proteins, lumican (the 37B core protein) and fibromodulin. These three proteins share approximately 35% amino acid identity and a number of conserved structural features. Northern hybridization and immunoblotting of tissue extracts found keratocan distribution to be more limited than that of lumican or fibromodulin. Keratocan is abundant in cornea and sclera and detected in much lesser amounts in skin, ligament, cartilage, artery, and striated muscles. Only in cornea was keratocan found to contain large, sulfated keratan sulfate chains. Keratocan, like lumican, is a core protein of a major corneal proteoglycan but is present in non-corneal tissues primarily as a nonsulfated glycoprotein.
Corpuz
L M
LM
Division of Biology, Kansas State University, Manhattan 66506-4901, USA.
Funderburgh
J L
JL
Funderburgh
M L
ML
Bottomley
G S
GS
Prakash
S
S
Conrad
G W
GW
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry; D002417:Cattle; D002478:Cells, Cultured; D011508:Chondroitin Sulfate Proteoglycans / Q000032:analysis / Q000097:blood* / Q000737:chemistry; D003001:Cloning, Molecular; D003315:Cornea / Q000166:cytology / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D000071235:Fibromodulin; D015870:Gene Expression; D015723:Gene Library; D007632:Keratan Sulfate / Q000032:analysis / Q000097:blood* / Q000737:chemistry; D000071234:Lumican; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010802:Phylogeny; D011509:Proteoglycans / Q000032:analysis / Q000096:biosynthesis* / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid
D002352:Carrier Proteins; D011508:Chondroitin Sulfate Proteoglycans; D016326:Extracellular Matrix Proteins; C490949:KERA protein, Bos taurus; D000071234:Lumican; D011509:Proteoglycans; D012333:RNA, Messenger; D000071235:Fibromodulin; D007632:Keratan Sulfate