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Sperm Lysozyme‐Like Protein 1 ( SLLP 1), an intra‐acrosomal oolemmal‐binding sperm protein, reveals filamentous organization in protein crystal form
Author(s) -
Zheng H.,
Mandal A.,
Shumilin I. A.,
Chordia M. D.,
Panneerdoss S.,
Herr J. C.,
Minor W.
Publication year - 2015
Publication title -
andrology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.947
H-Index - 43
eISSN - 2047-2927
pISSN - 2047-2919
DOI - 10.1111/andr.12057
Subject(s) - lysozyme , acrosome , glycan , biology , monomer , docking (animal) , protein structure , chemistry , crystallography , sperm , biophysics , glycoprotein , biochemistry , genetics , medicine , nursing , organic chemistry , polymer
Summary Sperm lysozyme‐like protein 1 ( SLLP 1) is one of the lysozyme‐like proteins predominantly expressed in mammalian testes that lacks bacteriolytic activity, localizes in the sperm acrosome, and exhibits high affinity for an oolemmal receptor, SAS 1B. The crystal structure of mouse SLLP 1 ( mSLLP 1) was determined at 2.15 Å resolution. mSLLP 1 monomer adopts a structural fold similar to that of chicken/mouse lysozymes retaining all four canonical disulfide bonds. mSLLP 1 is distinct from c‐lysozyme by substituting two essential catalytic residues (E35T/D52N), exhibiting different surface charge distribution, and by forming helical filaments approximately 75 Å in diameter with a 25 Å central pore comprised of six monomers per helix turn repeating every 33 Å. Cross‐species alignment of all reported SLLP 1 sequences revealed a set of invariant surface regions comprising a characteristic fingerprint uniquely identifying SLLP 1 from other c‐lysozyme family members. The fingerprint surface regions reside around the lips of the putative glycan‐binding groove including three polar residues (Y33/E46/H113). A flexible salt bridge (E46‐R61) was observed covering the glycan‐binding groove. The conservation of these regions may be linked to their involvement in oolemmal protein binding. Interaction between SLLP 1 monomer and its oolemmal receptor SAS 1B was modeled using protein–protein docking algorithms, utilizing the SLLP 1 fingerprint regions along with the SAS 1B conserved surface regions. This computational model revealed complementarity between the conserved SLLP 1/ SAS 1B interacting surfaces supporting the experimentally observed SLLP 1/ SAS 1B interaction involved in fertilization.