λgt11 clones encoding human prostatic acid phosphatase (PAP) (EC 3.1.3.2) were isolated from human prostatic cDNA libraries by immunoscreening with polyclonal antisera. Sequence data obtained from several overlapping clones indicated that the composite cDNAs contained the complete coding region for PAP, which encodes a 354‐residue protein with a calculated molecular mass of 41 126 Da. In the 5′‐end, the cDNA codes for a signal peptide of 32 amino acids. Direct protein sequencing of the amino‐terminus of the mature protein and its proteolytic fragments confirmed the identity of the predicted protein sequence. PAP has no apparent sequence homology to other known proteins. However, both the cDNA clones coding for human placental alkaline phosphatase and PAP have an alu‐type repetitive sequence about 900 nucleotides downstream from the coding region in the 3′‐untranslated region. Two of our cDNA clones differed from others at the 5′‐ends. RNA blot analysis indicated mRNA of 3.3 kb. We are continuing to study whether acid phosphatases form a gene family. as do alkaline phosphatases.
The chromosomal location of the gene encoding human prostate-specific acid phosphatase (ACPP) was determined by Southern blotting analysis of panels of human × rodent (mouse or Chinese hamster) somatic cell hybrids, using the PAP-1007 and PAP-1004EP ACPP cDNA probes. The ACPP gene was assigned to chromosome 3, which was confirmed by screening a chromosome 3-specific genomic library. Sublocalization of this gene was carried out using hybrids that had retained only various portions of human chromosome 3. The ACPP gene was found to segregate specifically with the chromosomal segment 3q21→qter. Analysis of Southern blots of Taq I-digested DNAs from unrelated individuals and members of large families from northern Finland revealed two simultaneous diallelic restriction fragment length polymorphisms (RFLPs), A and B, when using either PAP-1004EP or PAP-1006A ACPP cDNA probes, but not the 5’ flanking PAP-1007 probe. Allele frequencies for polymorphism A were .09 (A1) and .91 (A2), and for polymorphism B, .38 (B1) and .62 (B2). There appears to be only a very minor linkage disequilibrium (χ2 = 1.12, 0.35 > P > 0.25) between the two Taql RFLPs at the ACPP locus. For reasons presently unknown, homozygotes for polymorphism B appear to be overrepresented. These polymorphisms could be of importance in characterizing human prostate cancer.
Alignment of the amino-acid sequences of the human lysosomal acid phosphatase (LAP) and human prostatic acid phosphatase (PAP) yielded an extensive homology between the two mature polypeptide chains. In the overlapping part, which extends over the entire PAP sequence and the N-terminal 90% of the LAP sequence, the identity is 49.1%. The LAP has an additional C-terminal sequence, which is encoded by the last exon of the LAP gene. This sequence contains the transmembrane domain of LAP, which is lacking in the secretory PAP. All six cysteine residues as well as 20 out of 27 (LAP) and 26 (PAP) proline residues present in the overlapping part of the proteins are conserved, suggesting that they are involved in stabilization of the tertiary structure of both proteins. Only two out of 8 N-glycosylation sites in LAP and 3 in PAP are conserved, suggesting that the dense N-glycosylation of LAP is related to its function in lysosomes.
Die saure Phosphatase der Lysosomen und die saure Phosphatase der Prostata des Menschen sind homologe ProteineZusammenfassung: Der Vergleich der Aminosäuresequenz der lysosomalen sauren Phosphatase (LAP) und der sauren Prostata-Phosphatase (PAP) des Menschen ergab eine ausgeprägte Homologie für die reifen Formen beider Proteine. Im Überlappungsbereich, der sich über die gesamte PAP-Sequenz und die N-terminalen 90% der LAP-Sequenz erstreckt, beträgt die Identität 49,1 %. Die LAP trägt am C-Terminus eine zusätzliche Sequenz, die vom lezten Exon des LAP-Gens kodiert wird. Diese Sequenz enthält die Transmembrandomaine der LAP, die der sekretorischen PAP fehlt. Alle 6 Cysteinreste sowie auch 20 von 27 (LAP) bzw. 26 (PAP) Prolinresten, die im Überlappungsbereich beider Proteine vorhanden sind, sind konserviert. Das legt eine Beteiligung dieser Aminosäuren an der Stabilisierung der Tertiärstruktur beider Proteine nahe. Nur zwei von 8 TV-Glykosylierungsstellen in der LAP und 3 in der PAP sind konserviert. Dies legt nahe, daß die ausgeprägte 7V-Glykosylierung der LAP in Beziehung zur Funktion dieses Enzyms in den Lysosomen steht.
We have previously reported the identification and basic characterization of two biallelic TaqI RFLPs, A and B, of the 3’ end of the human ACPP locus in an unselected Finnish population (Winqvist et al., 1989). In the present investigation, a similar allelic distribution was observed in patients with prostatic cancer or benign hyperplasia. In addition, it was found that the DNA sequences generating RFLP-B are located further downstream from the RFLP-A sequences.
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