Fractionation of basic nuclear proteins of human sperm by zinc chelate affinity chromatography

Preparation of magnetic immobilized metal affinity separation media and its use in the isolation of proteins

A new method of pseudobiospecific protein isolation is developed and tested, which employs both metal affinity and magnetism as the basis for isolation. The chelating group iminodiacetic acid (IDA) has been coupled to the surface of magnetic agarose, and when charged with metal ions (Cu2+ or Zn2+) is capable of binding model proteins which display metal affinity, and of separating protein mixtures. Magnetic properties of the medium facilitated the batch recovery of the adsorbent, as losses are minimized by concentrating and retaining the separation medium with the aid of a magnet. Model proteins were used to characterize protein adsorption, capacity, and stability of IDA magnetic agarose. Recovery from a cell lysate was demonstrated by protein isolation from extracts of E. coli containing a target protein. Overall, this study effectively illustrates the engineering of separation media which combine several desired properties for the development of a new branch of metal affinity-based bioseparation.

Interaction of mammalian sperm nuclear protamines and peptides derived thereof with immobilized zinc

The interaction of mammalian and human protamines with zinc was studied by immobilized metal ion affinity chromatography (IMAC). The affinity of protamines containing blocked cysteine residues was found to correlate in part with the presence and number of histidine residues in the protamine structure: absence or low affinity of P1 protamines containing 0 or 1 histidine residue; high affinity of human P2 protamine containing 9 histidines. Nevertheless a fraction strongly retained on an IDA-Zn(II) column was observed for P1 protamines with one histidine in the N-terminal sequence (ram and boar protamines). The strong binding was found to be related to the presence of tyrosine, serine and threonine closely spaced to the histidyl side chain. In the case of human protamine P2, the strong retention on the IDA-Zn(II) column seems to result from the additive contribution of all the histidine residues of the molecule. Thus, strong retention of protamines in IMAC seems to depend on an additive contribution of amino-acid side chains: histidine, tyrosine, serine, threonine and perhaps arginine. The high affinity of protamines, more especially P2 protamines, for zinc suggests that this metal ion could play a role for their correct folding and binding to DNA.

Fixation for the 1990's: a review of needs and accomplishments

Neutral buffered formalin (NBF) has been the standard fixative in histopathology for many decades; however, new technologies and increasing time constraints have made this common fixative less widely applicable. The attributes of universal and ideal fixatives are reviewed and compared with those of NBF. On the strength of a growing body of literature and experience in the histopathology field, zinc formalin solutions are recommended as a functional replacement for NBF. Zinc formalin permits better morphological preservation and preserves immunoreactivity even after prolonged fixation times. Coordinated zinc ions are postulated to maintain macromolecules in their original three-dimensional conformation as formaldehyde forms addition products with them. Significant crosslinking and gross distortion of tertiary structure are thereby avoided.

Auto-antibodies to human sperm basic nuclear proteins in infertile and vasectomized men: characterization of antigens and epitopes recognized by antibodies

The sera of vasectomized men and of patients with immune infertility were used to study the antigens and epitopes of sperm nuclear proteins that bind antibodies in these sera. No reaction with sperm histones was observed except for one serum. P1, P2 protamines and pro-P2 protamines were recognized by auto-antibodies. Studies with peptides derived from P1 and P2 protamines and with mammalian protamines related to HP1 showed that antibodies are mainly specific for a folded protamine molecule, more especially antibodies from vasectomized men. These results disagree with the random coil model proposed for protamines by several previous works. A cross-reactivity between P1 and P2 protamines was observed only for the whole molecules and not for peptides derived from them. This observation suggests that the two classes of protamines, different in sequence, may have a similar folding and thereby may be functionally equivalent.

P2 protamines from human sperm are zinc -finger proteins with one CYS2/HIS2 motif

P1 (HP1) and P2 (HP2, HP3, HP4) protamines were isolated from human sperm nuclei in the reduced form and their interaction with zinc and cobalt was studied. One zinc atom per molecule of P2 protamines but not of P1 protamine was found. Absorption spectra of P2 protamines with cobalt were characteristic of a tetrahedral complex involving two histidine and two cysteine residues and with one cobalt per molecule. A tetrahedral complex was found neither in P1 protamines nor in P2 protamines alkylated at cysteine or at histidine residues. The zinc finger motif Cys2/His2 of P2 protamines may play a role in stabilization of human sperm chromatin and in inhibition of transcription.

The immune response to synthetic peptides of human protamines HP1 and HP2

Peptides representing the amino-terminal sequence of protamines HP1 (sequence 1-12) and HP2 (sequence 1-11), the two major nuclear proteins of human sperm, have been synthesized. Rabbits were immunized either with peptide conjugated with a carrier or with free peptide. The resulting antisera were examined for their capacities to bind the homologous peptide, other peptides from protamines HP1, HP2, from ram protamine, a protein resembling HP1, and finally with the whole protamine. Only free peptides were immunogenic. Antisera were found to react with the homologous peptide, but also with some other peptides. More especially, antibodies to peptide HP1 1-12 were found to recognize an epitope shared by the homologous peptide, peptide HP1 37-49 and peptide 1-12 of ram protamine. The common antigenic determinant seems to depend on the conformation of the peptides, rather than strictly related to common sequences. Anti-peptide antibodies react poorly and in a non-specific manner with the parent protein. The failure of reactivity with the protamines strongly suggest that these small basic proteins are folded and probably globular molecules in contrast with the totally random model postulated by several previous works.