Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
. 1979 Aug;76(8):3819-23.
doi: 10.1073/pnas.76.8.3819.

Primary structure of the NH2-terminal extra piece of the precursor to human placental lactogen

L M Sherwood, Y Burstein, I Schechter
Comparative Study

Primary structure of the NH2-terminal extra piece of the precursor to human placental lactogen

L M Sherwood et al. Proc Natl Acad Sci U S A. 1979 Aug.

Abstract

The cell-free translation product of human placental lactogen mRNA is a precursor molecule larger than the mature hormone that circulates in plasma. To determine the structure of pre-placental lactogen, the poly(A)-rich RNA fraction of term placenta was isolated and translated in a wheat germ cell-free system. The mRNA programmed the synthesis of a major protein, 3000 daltons larger than placental lactogen, that was specifically precipitated by hormone antibodies. The immunoprecipitated protein was labeled separately with 20 radioactive amino acids and subjected to sequence analysis. The results showed the synthesis of pre-placental lactogen in which an extra piece 25 residues long preceded the NH2 terminus of the mature protein. The structure of the extra piece is as follows: Met-Pro-Gly-Ser-Arg-Thr-Ser-Leu-Leu-Ala-Phe-Ala-Leu-Leu-Cys-Leu-Pro-Trp-Leu-Gln-Glu-Ala-Gly-Ala-. Met1 is the initiator residue because only initiator [35S]Met-tRNAMet1, but not internal [35S]Met-tRNA2Met, donated NH2-terminal methionine. The structure of the extra piece showed little homology with that of unrelated hormones but striking homology (64%) with the extra piece of rat pre-growth hormone. Most amino acid substitutions involved a single base change in the codon. Mature human placental lactogen and rat growth hormone have 59% homology in sequence. Thus, our findings provide additional evidence to support the common evolutionary origin of these hormones, not only of the mature proteins but also of the extra piece segments.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

References

    1. Endocrinology. 1965 Mar;76:369-81 - PubMed
    1. Endocrinology. 1962 Aug;71:209-20 - PubMed
    1. Eur J Biochem. 1978 Aug 15;89(1):187-93 - PubMed
    1. Proc Natl Acad Sci U S A. 1977 Jul;74(7):3014-8 - PubMed
    1. Proc Natl Acad Sci U S A. 1978 Jun;75(6):2616-20 - PubMed

Publication types

LinkOut - more resources