We report the identification of ligands for Tyro 3 (alternatively called Sky, rse, brt, or tif) and Axl (alternatively, Ark or UFO), members of a previously orphan family of receptor-like tyrosine kinases. These ligands correspond to protein S, a protease regulator that is a potent anticoagulant, and Gas6, a protein related to protein S but lacking any known function. Our results are reminiscent of recent findings that the procoagulant thrombin, a protease that drives clot formation by cleaving fibrinogen to form fibrin, also binds and activates intracellular signaling via a G protein-coupled cell surface receptor. Proteases and protease regulators that also activate specific cell surface receptors may serve to integrate coagulation with associated cellular responses required for tissue repair and growth, as well as to coordinate protease cascades and associated cellular responses in other systems, such as those involved in growth and remodeling of the nervous system.

A 1434 base pair human liver cDNA coding for the entire alpha 1-antitrypsin protein has been isolated and sequenced. Translation of the coding region into amino acids reveals a precursor molecule which contains a 24 amino acid signal peptide and 394 amino acids present in the mature polypeptide chain. The human gene for the S variant of alpha 1-antitrypsin has also been subcloned and sequenced. The gene is composed of 10226 nucleotide bases and is approximately equimolar for all 4 nucleotides. The gene contains four intervening sequences (introns) and 5' and 3' noncoding regions which are 54 and 79 nucleotides in length, respectively. A 5.3-kilobase intron exists in the 5' noncoding region and contains a 143 amino acid open reading frame, an Alu family sequence, and a pseudo transcription initiation region. No significant differences in base composition are seen between the introns and those regions corresponding to coding regions of the corresponding mRNA (exons). A sequence of 1951 nucleotides flanking the 5' end of the gene has also been determined and contains a "TATA" box sequence (TTAAA-TA) 21 nucleotides upstream from the proposed transcription start site. Comparison of the gene sequence with the cDNA sequence reveals a single base substitution (A----T), which results in a Glu----Val substitution at position 264 in the S variant protein. The position and size of introns, the overall base composition, and the codon preference for the alpha 1-anti-trypsin gene differ from those for the chicken ovalbumin gene even though the two proteins belong to a common protein family, as judged by amino acid sequence homology.

No abstract

Protein C deficiency (McK. No. 176860) is an autosomally inherited disorder that is associated with a high risk of recurrent venous thrombosis. Until recently, the analysis and diagnosis of protein C deficiency has been reliant upon the laboratory measurement of plasma protein C antigen and activity levels. Diagnostic uncertainty ffioy, however, arise due to the overlap between the ranges of values characteristic of the normal and deficiency states. Diagnostic uncertainty may be further increased if the patient is already undergoing ordl anticoagulant therapy with vitamin K antagonists such as Coumarin drugs that block y-carboxylation. Moreover, this type of laboratory analysis provides little or no information as to the nature of the underlying defect or its mode of inheritance. The utility of a molecular genetic approach to the study of protein C deficiency lies in its ability to provide accurate and reliable information both on the specific genetic lesion(s) involved and on the genotypes of the propositae and their relatives. Precise knowledge of the underlying genetic abnormalities may also provide starting points for the structure-function analysis of the protein C gene (the effect of promoter mutations on gene expression) and molecule (protein C variants). With the advent of rapid and efficient techniques for the analysis of DNA at the single nucleotide level, such an approach has become feasible in an increasing number of laboratories. Here, we present an up-todate listing of mutations in the protein C gene so far identified. Only a small proportion of these lesions have been published in any detail. All unreviewed and unpublished data must be regarded as preliminary. Inclusion in the database should not preclude more detailed publication elsewhere. Structure and Function of Protein C Protein C, a vitamin K-dependent glycoprotein and zymogen of a serine protease, plays an important regulatory role in haemostasis (1, 2). Synthesized in the liver as a single-chain polypeptide, it undergoes post-translational modification (B-hydroxylation, y-carboxylation and glycosylation) to give rise

Human genomic clones that span the entire protein S expressed gene (PS alpha) and the 3' two-thirds of the protein S pseudogene (PS beta) have been isolated and characterized. The PS alpha gene is greater than 80 kilobases in length and contains 14 introns and 15 exons, as well as 6 repetitive "Alu" sequences. Exons I and XV contain 112 and 1139 bp 5' and 3' noncoding segments in addition to the amino and carboxyl termini, respectively. Exons I-VIII encode protein segments that are homologous to the vitamin K dependent clotting proteins and are bounded by introns whose position and type are identical with other members of this protein family. Exons IX-XV encode protein segments homologous to sex hormone binding globulin (SHBG) and are bounded by introns of identical type and position as in the SHBG gene. Genomic clones for the PS beta gene cover a distance of greater than 55 kilobases and contain segments corresponding to amino acids 46-635 of the mature protein and the 1.1-kb 3' noncoding region of the cDNA. The presence of multiple base changes in the coding portions of this gene, resulting in termination codons and frame shifts, suggests that it is a pseudogene. Comparison of DNA sequences for the two genes reveals 97% identity for coding and 3' noncoding, and 95.4% for intronic regions, suggesting divergence of the two genes is a relatively recent event.