rabbit chondrocytes were used as the chondrocytes . rib cartilage growth plates of 4 weeks old new zealand rabbits were surgically dissected out and then rib cartilage growth plates were treated with trypsin and collagenase according to the method by kato et al . ( op cit .) to isolate chondrocytes . according to this procedure , there were obtained chondrocytes of about 4 × 10 6 cells per rabbit . these chondrocytes were sprayed onto culture dishes , each having a culture area of 500 cm 2 , at about 8 × 10 5 cells per dish , 100 ml of deme medium containing 10 % fetal calf serum was added and incubation was carried out at 37 ° c . under atmosphere of 5 % co 2 and 95 % air . the chondrocytes obtained as described in the above ( 1 ) were incubated until they became confluent , the cultured chondrocytes were washed twice with physiological saline as they adhered onto the culture dishes and then the chondrocytes were recovered by means of a scraper . the cells thus recovered were suspended in a four times volume of a cell - disruption buffer ( 0 . 25m sucrose , 5mm mops / koh ph 7 . 4 , 1 mm edta , 1 mm pmsf , 10μm pepstatin ) and the cells were disrupted on ice by means of a homogenizer ( available from polytron inc .). the disrupted cell suspension was treated by means of a glass homogenizer using a teflon rod to disrupt the cell more finely , centrifugation was performed at 4 ° c . and 105 , 000 × g for one hour and the supernatant was discarded . the precipitate was resuspended in 24 ml of the same cell - disruption buffer and then cell - disruption was again performed using the glass homogenizer and a teflon pestle . the cell - disrupted suspension was overlapped on the solutions of sucrose equilibrium density - gradients of 17 %/ 40 % previously placed into a centrifuge tube and sedimentation equilibrium centrifugation was performed at 4 ° c . and 200 , 000 × g for 1 . 5 hours . thereafter , the membrane proteins separated at the interface between 17 % sucrose and 40 % sucrose were isolated . ( 3 ) isolation of concanavalin a - binding glycoproteins the above - mentioned membrane fraction was subjected to the following procedure in order to remove the sucrose remaining in the fraction . the above - mentioned membrane fraction was diluted with a buffer ( 5 mm mops , ph 7 . 4 ) and then centrifuged at 4 ° c . and 100 , 500 × g for one hour to remove the supernatant . the precipitate was dissolved in a buffer for solubilization ( 10 mm tris - hcl ( ph 7 . 4 ), 10 μm apmsf , 10 μm pepstatin ) containing 1 % deoxycholic acid . then , for obtaining the glycoprotein specifically binding concanavalin a , the fractions binding to a wheat germ lectin , was removed from the resultant solution . more specifically , the solution was developed using the wheat germ lectin - wga - sepharose 6 mb column ( 4 cm × 2 . 5 cm , available from pharmacia ab ) previously equilibrated with the buffer for solubilization to recover the non - binding fractions . thereafter , the fraction not bound to the wheat germ lectin - sepharose column was developed with the concanavalin a sepharose column ( 5 cm × 1 . 5 cm , available from pharmacia ab ) previously equilibrated with the buffer for solubilization , the column was washed with the same buffer as above and the bound glycoproteins were eluted with the same buffer containing 0 . 5m methyl - α - mannopyranoside . the eluted fraction was enclosed into a dialysis tube , dialyzed against a dialysis buffer ( 10mm tris - hcl , ph 7 . 4 ) and then concentrated with an ultrafiltration membrane ( available from centricon - aminon inc .). the concentrated sample was subjected to electrophoresis using 4 %/ 20 % gradient gels under a reduced condition according to the method by lammli . identification of the proteins were performed with coomassie brilliant blue ( cbb ) or silver staining . as a result , there was confirmed the presence of 20 or more types of the glycoproteins having different molecular weights . ( 4 ) extraction of cmp isolated with the gradient gels from the said gels of the proteins isolated by means of the said electrophoresis , the band having a molecular weight of about 76 kda was cut out together with the gel thereof in the state of non - cbb staining or silver staining and then the aimed protein was extracted from the gel using an electroeluter ( available from bio - rad laboratories , inc . u . s . a .). according to the aforesaid procedure , there were obtained the homogeneous glycoproteins having a molecular weight of about 76 kda , which was named &# 34 ; chondrocyte membrane protein &# 34 ; abbreviated as cmp . ( 5 ) enzymatic deglycosilation of cmp for endoglycosidase reactions ( c . maillard et al . ; bone vol . 13 , pages 257 - 264 , 1992 ), purified cmp was incubated with endoglycosidase h ( endo h ), endoglycosidase f ( endo f ) or n - glycosidase f ( ngf ) ( boehringer mannheim biochemica , germany ). purified cmp 0 . 5 μg was incubated with 20 μl of endo h assay buffer ( 8 mu endo h , 50 mm sodium phosphate , ph 5 . 6 , 50 mm edta , 0 . 5 mm pmsf ), endo f assay buffer ( 40 mu endo f , 50 mm sodium phosphate , ph 5 . 6 , 50 mm edta , 0 . 5 % nonident p40 , 0 . 2 % sds , 1 % mercaptoethanol ) or ngf assay buffer ( 5 mu ngf , 45 mm potassium phosphate , ph 7 . 4 , 50 mm edta , 0 . 5 % nonident p40 , 2 % sds , 1 % 2 - mercaptoethanol ) for 5 hr . or overnight at 37 ° c . control incubations were carried out in the absence of enzymes . samples were boiled for 30 min . digested protein was analyzed on sds - page with silver stain to determine molecular weight changes . the results are shown in fig2 . fig2 shows endoglycosidase digestion of purified cmp . lanes 1 and 12 show high and low molecular markers , respectively . lane 2 shows the purified cmp . lanes 3 , 6 and 9 show endoglycosidase without cmp . lanes 4 , 7 , 10 and 5 , 8 , 11 show the electrophoresis patterns when cmp was incubated with endo h , ngf and endo f for 5 hr . and overnight at 37 ° c ., respectively . incubation of cmp with endo h or ngf resulted in a reduction of the molecular weight of the protein from 76 kda to 67 kda , indicating removal of carbohydrate . however , endo f did not result in molecular weight change of the glycoprotein . ( 1 ) determination of the n - terminal amino acid sequence of cmp the amino acid sequence of n - terminus of cmp was determined according to the following procedure . more specifically , the proteins in the sds - page gel obtained according to the procedure as described in example 1 ( 3 ) were electrically transcripted onto a pvde membrane and stained with 1 % acetic acid and 0 . 2 % ponceau s to confirm the band of individual protein and then marked on the membrane . then , the stained membrane was decolorized with a 0 . 5 mm sodium hydroxide solution , the cmp - transcripted part of the pvde membrane was cut out and the n - terminal amino acid sequence was determined by means of an amino acid analyzer ( available from applied biosystems , inc ., u . s . a .). seq id no . 1 shows the amino acid sequence of n - terminus as determined . in the sequence , &# 34 ; xaa &# 34 ; does mean that the amino acid residues were not determined . ( 2 ) determination of the internal amino acid sequence of cmp the peptide mapping of cmp was performed according to &# 34 ; a practical guide to protein and peptide purification for microsequencing &# 34 ; ( academic press inc ., 1989 ). homogenous cmp ( 20 μg ) was reduced in 50 μl of 8m urea and 0 . 4m ammonium bicarbonate ph 8 . 0 , containing 45 mm dithiothreitol for 15 rain at 50 ° c . carboxymethylation was performed by adding 5 μl of 100 mm iodoacetamide for 15 min at room temperature . 140 μl of water and trypsin ( 3 mu / mg protein ) was added to the reaction mixture . the digestion was allowed to proceed for 24 hr . at 37 ° c . peptide mapping was performed on c2 / c18 reverse phase column linked to smart system chromatography ( pharmacia inc ., sweden ). peptides were eluted with a gradient of 0 % - 100 % solvent b ( 100 % acetonitrile in 0 . 12 % trifluoroacetic acid ) over 110 min at a flow rate of 0 . 1 ml / min . elution of the peptides from the column was monitored by measuring absorbance at 215 nm . 4 peptide fragments were isolated and named t1 , t2 , t3 and t4 , respectively . their amino acid sequences were determined by 476a protein sequencer ( applied biosystems , inc ., u . s . a .) and shown in the sequence listing . t1 is shown in seq id no : 2 ; t2 is shown in seq id no : 3 ; t3 is shown in seq id no : 4 ; and t4 is shown in seq id no : 5 . comparison of cmp found in chondrocytes and fibroblast - like cells derived by dedifferentiation with a retinoic acid the chondrocytes isolated as described in example 1 ( 1 ) was treated with a retinoic acid to dedifferentiate to fibroblast - like cells . more specifically , to the cultured broth of chondrocytes obtained as described in example 1 ( 1 ) was added a retinoic acid in the form of its ethanolic solutions so as to be final concentrations of 0 , 0 . 01 μm , 0 . 1 μm and 1 μm , respectively , and then the incubation was performed for 96 hours . the chondrocytes have a weak cell - expanding ability and a spherical shape and , where a retinoic acid is added , they were dedifferentiated to fibroblast - like cells so that they can have an increased expanding ability to take a cellular morphology of being flat and expanded . it may be established upon such morphological changes whether or not dedifferentiation might be performed , and the dedifferentiation was also confirmed by this experiment . also , it was confirmed that the dedifferentiation level may depend upon the concentration of a retinoic acid and the period of time for treatment . on each of the chondrocytes incubated with the various concentrations of a retinoic acid added as described above , cells were recovered according to the procedure as described in example 1 ( 2 ) to obtain membrane proteins . then , the concanavalin a - binding glycoprotein fraction was obtained according to the procedure as described in example 1 ( 3 ) and its electrophoresis pattern was compared using sds - page . the results are shown in fig1 . fig1 shows a comparison of cmp &# 39 ; s found in chondrocytes and fibroblast - like cells derived by dedifferentiation . lane 1shows the electrophoresis pattern when no retinoic acid was added , and lanes 2 , 3 and 4 show the electrophoresis patterns when a retinoic acid was added to the medium at final concentrations of 0 . 01 μm , 0 . 1 μm and 1 μm , respectively . molecular weights are shown on the left side of lanes , while the location of cmp is shown on the right side of lanes together with its molecular weight . thus , it was confirmed that cmp disappeared depending upon the concentrations of a retinoic acid added . cmp disappeared together with dedifferentiation , namely , dedifferentiation to fibroblast - like cells . the gel band containing cmp obtained as described in example 1 ( 4 ) was cut out together with its gel portion , homogenized and subcutaneously administered to mice . at 3 weeks after the administration , partial blood samples were collected to confirm a sufficiently high level of the antibody valence to cmp and then the serum was collected to obtain anti - cmp antiserum . the specific expression of cmp in chondrocytes was further investigated using various organs or cells according to western blot technique with the anti - cmp antiserum obtained as described in example 4 . more specifically , the membrane proteins were obtained from 6 types of rabbit organs ; kidney , liver , brain , testis , intestine and spleen , and rabbit cultured fibroblasts , respectively according to the procedure as described in example 1 ( 2 ). the membrane proteins above were individually investigated for the presence or absence of cmp according to western blot technique to confirm that cmp is not found in all fractions , which proved that cmp is a protein specifically expressed in chondrocytes . __________________________________________________________________________sequence listing ( 1 ) general information :( iii ) number of sequences : 5 ( 2 ) information for seq id no : 1 :( i ) sequence characteristics :( a ) length : 15 amino acids ( b ) type : amino acid ( d ) topology : linear ( ii ) molecule type : peptide ( ix ) feature :( a ) name / key : peptide ( b ) location : 6 .. 7 ( d ) other information : / note =&# 34 ; xaa is an unknown aminoacid .&# 34 ;( xi ) sequence description : seq id no : 1 : servalgluvalargxaaxaathralasergluproproglngln151015 ( 2 ) information for seq id no : 2 :( i ) sequence characteristics :( a ) length : 18 amino acids ( b ) type : amino acid ( d ) topology : linear ( ii ) molecule type : peptide ( ix ) feature :( a ) name / key : peptide ( b ) location : 16 ( d ) other information : / note =&# 34 ; xaa is an unknown aminoacid .&# 34 ;( xi ) sequence description : seq id no : 2 : histhrthrtyrpheaspasnthrasnglyhisasnprogluproxaa151015alaala ( 2 ) information for seq id no : 3 :( i ) sequence characteristics :( a ) length : 16 amino acids ( b ) type : amino acid ( d ) topology : linear ( ii ) molecule type : peptide ( xi ) sequence description : seq id no : 3 : thrvalglytrpasnvalprovalglytyrleuvalaspserglyarg151015 ( 2 ) information for seq id no : 4 :( i ) sequence characteristics :( a ) length : 20 amino acids ( b ) type : amino acid ( d ) topology : linear ( ii ) molecule type : peptide ( ix ) feature :( a ) name / key : peptide ( b ) location : 18 ( d ) other information : / note =&# 34 ; xaa is an unknown aminoacid .&# 34 ;( xi ) sequence description : seq id no : 4 : thrthrtyrglnaspthrleuglyproasptyrvalalaalaleuglu151015glyxaaglnser20 ( 2 ) information for seq id no : 5 :( i ) sequence characteristics :( a ) length : 9 amino acids ( b ) type : amino acid ( d ) topology : linear ( ii ) molecule type : peptide ( xi ) sequence description : seq id no : 5 : tyrtyrasptyrserglyalaphearg15__________________________________________________________________________