Gene

  A molecular mass (Mr) of purified rhSCGF-α is 45 kDa on SDS-PAGE (below) (11) (Table and Figure), relatively larger than the calculated Mr of 33,534 Da. Digestion of rhSCGF with endo-O-glycosidase and sialidase reduces the Mr of 45 kDa to 40kDa (Figure; lane 5), implicating that rhSCGF from CHO cells is modified by a possible post-translational O-glycosylation including sialic acids, while no N-glycosylation site is deduced from scgf cDNA. SCGF is actually demonstrated to be O-glycosylated at Thr69 by N-acetylgalactosamine (433).

	Molecular mass (kDa)
	CHO cell product	E. coli product
hSCGF-α	45	33.9
hSCGF-β	29	25

   Isoelectric point of SCGF is predicted in silico at Phosphosite (Table).

	hSCGF	mSCGF	rSCGF
pI	5.06	4.91	5.28(5.14)

 
  Silver-stained SDS-PAGE of purified rhSCGF-α after
digestion with endo-O-glycosidase and/or sialidase. (11)
Lane 1, molecular mass markers; lane 2, purified rhSCGF-α; lane 3, rhSCGF-α digested with sialidase; lane 4, rhSCGF-α digested with endo-O-glycosidase; lane 5, rhSCGF-α digested with endo-O-glycosidase in the presence of sialidase; lane 6, sialidase alone; lane 7, endo-O-glycosidase alone; lane 8, endo-O-glycosidase and
sialidase. An arrowhead indicates the rhSCGF-α band.

Protein

  Recombinant SCGF is produced from pAGE-SCGF-α-transfected CHO cells (11) or E. coli, the latter of which is commercially available (see Materialssection).

  The NH₂-terminal aa sequence of rhSCGF-α is ARGAEREWEG, alanine of which corresponds to the 22nd A of the aa sequence deduced from scgf cDNA. Therefore a 21 aa signal peptide MQAAWLLGALVVPQLLGFGHG is removed to make up secreted mature SCGF (11).

  SCGF interacts with splice variant 2 but not with splice variant 1 of methionine adenosyltransferase 2Β up-regulated in colon cancer cell line, RKO (257), which could regulate transcription and give a growth advantage to cancer cells.

  Listed below are accession numbers of SCGF in the protein database.

Species	Accession Number (UniProtKB/TrEMBL/Swiss-Prot/)
Homo sapiens Human	Q9Y240B2RAD4Q5U0B9ENSP00000250340
Pan troglodytes Chimpanzee	ENSPTRP00000019500
Pongo pygmaeus Orangutan	ENSPPYP00000011522
Macaca mulatta Macaque	ENSMMUP00000003227
Mus musculus Mouse	O88200ENSMUSP00000004587
Rattus norvegicus Rat	O88201ENSRNOP00000025949
Bos Taurus Cow	A5D7L1ENSBTAP00000007326
Equus caballus Horse	ENSECAP00000017370
Canis familiaris Dog	ENSCAFP00000004325
Tursiops truncatus Dolphin	ENSTTRP00000012242
Cavia porcellus Guinea Pig	ENSCPOP00000021210
Dipodomys ordii Kangaroo rat	ENSDORP00000012818
Echinops telfairi Lesser hedgehog tenrec	ENSETEP00000014130
Microcebus murinus Mouse Lemur	ENSMICP00000002075
Monodelphis domestica Opossum	ENSMODP00000017642
Pteropus vampyrus Megabat	ENSPVAP00000013212
Myotis lucifugus Microbat	ENSMLUP00000007912
Ochotona princeps Pika	ENSOPRP00000006723
Spermophilus tridecemlineatus Squirrel	ENSSTOP00000005627
Ornithorhynchus anatinus Platypus	ENSOANP00000006207
Xenopus tropicalis X.tropicalis	ENSXETP00000038282
Oryzias latipes Medaka	ENSORLP00000022025
Takifugu rubripes Fugu	ENSTRUP00000009548
Tetraodon nigroviridis Tetraodon	ENSTNIP00000022352
Rhincodon typus Whale shark	XP_020367030

  SCGF is actually stable in a trimeric form (data not shown) as is tetranectin molecularly akin to SCGF (12).  
  Homotrimer forms a triple α-helical coiled coil with a consensus CRD structure  of  6 β-strands, 2 α-helices and 4 Ca²⁺-harboring loops (14-16).

  3D structures of human, mouse and rat SCGF have been deposited in AlphaFold Protein Structure Database.

← Human SCGF (*N-terminal) (modified from AlphaFold)