Table 1.

Exon-intron organization of the human LDL receptor gene. The nucleotide sequences of exon-intron junctions were determined by the enzymatic method (36) with the use of recombinant bacteriophage M13 clones containing genomic fragments as templates and the universal primer (37) together with a family of 25 LDL receptor–specific oligonucleotide primers. Exons 1 to 3 and 5 to 17 were sequenced in their entirety; intron 13 was sequenced in its entirety. Exon sequences are in capital letters; intron sequences are in lowercase letters. The number shown immediately below the DNA sequence denotes the nucleotide position at which the intron interrupts the LDL receptor mRNA (4). The numbers shown in parentheses in the extreme right-hand column denote the position of the indicated amino acid in the mature LDL receptor protein (4). The size for intron 1 is a minimal estimate based on concordance between data obtained from Southern blotting experiments with genomic DNA and data obtained from the restriction maps of the genomic clones. Approximately 2 kb of intron 6 was present in the genomic clones (Fig. 1); the amount of DNA not present in the genomic clones (0.7 kb) was estimated by Southern blotting of genomic DNA using probes derived from exons 6 and 7.

Exon num- ber	Exon size (bp)	Sequence at exon-intron junction		Intron length (kb)	Amino acid inter- rupted
		5′ Splice donor	3′ Splice acceptor
1	145–160			>10	Val (2)
2	123			2.5	Leu (43)
3	123			2.4	Pro (84)
4	381			0.95	Ala (211)
5	123			0.85	Val (252)
6	123			2.7	Gly (293)
7	120			0.45	Asp (333)
8	126			1.2	Gly (375)
9	172			0.9	Ser (432)
10	228			2.6	Gly (508)
11	119			0.6	Asp (548)
12	140			3.0	Glu (594)
13	142			0.134	Gly (642)
14	153			2.8	Glu (693)
15	171			5.5	Ala (750)
16	78			1.4	Val (776)
17	158			1.7	Ser (828)
18	2535