Question

How about positive charges? What happens when two lysines get too close to each other in terms of changing their PKas?

Answer 1

Acids release H⁺ ions that can turn neutral molecules into positively charged ions, while bases can attract H⁺ ions from neutral molecules to produce negatively charged ions. Amino acid contain nitrogen and resemble ammonia, which is a base  pKa's are high enough that they tend to bind protons, gaining a positive charge in the process.At a pH inferior to their pK, the lysine, arginine and histidine side chains accept an H⁺ ion (proton) and are positive charged

The pKa of a a proton is the log of the ratio of its ionized form to its unionized form in water.pKa is the negative base-10 logarithm of the acid dissociation constant of a solution.Lysine is an essential amino acid for the nutrition of humans.

Lysine  an essential amino acid. The ε-NH₂(pK′=10.53) is protonated at physiological pH. The lysyl side chain forms ionic bonds with negatively charged groups of acidic amino acids. The basic amino acids, lysine highly polar.pK_a values measured for naturally occurring internal Lys residues higher pK_a renders the lysyl side chains effectively less nucleophilic butin enzyme active centers can lower the pKa of the lysyl side chain such that it becomes reactive.